Carp Dominate Fish Communities Managing the Impacts of Carp Throughout Many Waterways in South- Eastern Australia

Home , Alburninae, Bala shark, Crucian carp, Cultrinae, Darling River hardyhead, Giant salmon carp

Managing the Impacts of

Introduced carp dominate fish communities Managing the Impacts of Carp throughout many waterways in south- eastern Australia. They also occur in Carp Western Australia and Tasmania and have the potential to spread through many more of Australia’s water systems. Carp could eventually become widespread throughout the country. Carp are known to damage aquatic plants and increase water turbidity but their impacts on native fish species are not yet clear. Carp are also a commercial and recreational fishing resource. Managing the Impacts of Carp provides a comprehensive review of the history of carp in Australia, their biology, the damage they cause and community attitudes to these problems and their solutions. Key strategies for successful carp management are recommended by the authors who are scientific experts in carp management. These strategies are illustrated by case studies. Managing the Impacts of Carp is an essential guide for policy makers, land and water managers, carp fishers and all others interested in carp management.

AGRICULTURE, FISHERIES AND FORESTRY - AUSTRALIA Managing the Impacts of Carp

John Koehn, Andr ea Brumley and Peter Gehrke

Scientific editing by Mary Bomfor d

Published by Bureau of Rural Sciences, Canberra © Commonwealth of Australia 2000 ISBN 0 644 29240 7 (set) ISBN 0 642 73201 9 (this publication) This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without prior written permission from the Bureau of Rural Sciences. Requests and inquiries concerning reproduction and rights should be addressed to the Executive Director, Bureau of Rural Sciences, PO Box E11, Kingston ACT 2604.

Published by: Copies available fr om: Bureau of Rural Sciences AFFA Shopfront PO BOX E11 GPO Box 858 Kingston ACT 2604 Canberra ACT 2601 Ph: 02 6272 4282 Phone: 02 6272 5550 Fax: 02 6272 4747 Fax: 02 6272 5771 Internet: http://www.brs.gov.au Email: [email protected]

The Bureau of Rural Sciences is a professionally independent scientific bureau within the Department of Agriculture, Fisheries and Forestry – Australia (AFFA). Its mission is to provide first-class scientific research and advice to enable the department to achieve its vision — rising national prosperity and quality of life through competitive and sustainable agricultural, fisheries and forestry industries.

The Commonwealth and all persons acting for the Commonwealth in preparing this booklet disclaim all responsibility and liability to any person arising directly or indirectly from any person taking or not taking action based upon the information in this booklet. Affiliations: Authors: John Koehn, Department of Natural Resources and Environment, Victoria Andrea Brumley, Forestech, East Gippsland Institute of TAFE Peter Gehrke, NSW Fisheries Office of Conservation Editor: Mary Bomford, Bureau of Rural Sciences, Canberra. Typeset by Lisa Curtin. Printed by Pirie Printers. Preferr ed way to cite this publication: Koehn, J., Brumley, A. and Gehrke, P. (2000) Managing the Impacts of Carp. Bureau of Rural Sciences (Department of Agriculture, Fisheries and Forestry – Australia), Canberra.

Printed by Pirie Printers Pty limited For ewor d

Carp (Cyprinus carpio) have become the The principles underlying the strategic man- most abundant large freshwater fish in agement of vertebrate pests have been Australia and are considered a problem described in Managing Vertebrate Pests: because of their perceived impacts on water Principles and Strategies (Braysher 1993) quality, soft-leaved aquatic plants and native and in Australia’s Pest Animals: New fish populations through competition and Solutions to Old Problems (Olsen 1998). The lowering habitat quality. Carp are also val- emphasis is on managing of pest damage ued by those who fish them commercially or rather than on simply reducing pest density. for recreation, and carp are used to produce The guidelines recommend that, wherever fertiliser, pet food and bait and small quanti- practical, management should concentrate ties are sold in Australia and exported to on achieving clearly defined economic or European markets for human consumption. conservation benefits. There is little reliable information about the This publication complements the National extent and nature of many of the problems Management Strategy for Carp Control caused by carp and how they can best be (NMSCC) developed by the Carp Control solved. This has led to diverse views about Coordinating Group (CCCG). The NMSCC carp management. describes a framework for a uniform national approach to the management of carp. Both Whether carp have simply taken advantage documents have been produced under the of poor habitat condition or whether they are Federal Government's Natural Heritage a cause of it is subject to much debate. The Trust. reality is probably a combination of the two. Regardless, assessing and managing the The approach to managing carp damage set impacts of carp cannot be considered in iso- out in these guidelines has been approved by lation from other water management issues. the Standing Committees on: Agriculture and Carp management is just one of many factors Resource Management; Conservation; and which influence water quality and aquatic Fisheries and Aquaculture. biodiversity. These guidelines will help policy-makers This publication is one in a series of Bureau and managers reduce the damage to water of Rural Sciences pest animal management resources and the naural environment guidelines which provides natural resource caused by carp through the use of scientifi- users, managers, advisers and funding agen- cally-based management that is humane, cies with ‘best practice’ national guidelines cost-effective, and integrated with ecologi- for managing the economic and environ- cally sustainable development. mental damage caused by carp. Others in the series include guidelines for managing feral horses, rabbits, foxes, feral goats, feral pigs, rodents and wild dogs.

Peter O’Brien

Executive Director Bureau of Rural Sciences

Managing the Impacts of Carp iii

Contents

FOREWORD iii ACKNOWLEDGMENTS ix SUMMARY 1 INTRODUCTION 7

1. TAXONOMY AND HISTORY OF INTRODUCTION 11 Summary 11 1.1 Family Cyprinidae 11 1.2 Carp in Europe and Asia 12 1.3 Introduction of Cyprinids to Australia 17 1.4 Genetic strains of carp in Australia 19

2. DISPERSAL, DISTRIBUTION AND ABUNDANCE 23 Summary 23 2.1 Factors contributing to the spread of carp 23 2.2 Distribution and abundance 29

3. BIOLOGY AND ECOLOGY 33 Summary 33 3.1 General description 33 3.2 Habitats 35 3.3 Feeding behaviour and diet 39 3.4 Population dynamics 40 3.5 Ecological interactions 52 3.6 Current research 58

4. COMMUNITY ATTITUDES AND EXPECTATIONS 61 Summary 61 4.1 Attitudes from the northern hemisphere 61 4.2 Public attitudes in Australia 62 4.3 Attitudes of environmental authorities in Australia 64 4.4 Conservation groups 65 4.5 Indigenous communities 67 4.6 Animal welfare and animal rights 68 4.7 Commercial fishing industry 69 4.8 Other businesses 70 4.9 Recreational fishers 71 4.10 Carp for human consumption 74 4.11 Carp action groups and catchment management 74

Managing the Impacts of Carp v 5. ECONOMIC AND ENVIRONMENTAL IMPACTS AND COMMERCIAL USE 77 Summary 77 5.1 Introduction 77 5.2 Economic impacts 78 5.3 Environmental impact 79 5.4 Resource value and commercial use 88

6. PAST AND CURRENT MANAGEMENT 99 Summary 99 6.1 Public pressure for action 99 6.2 National management 99 6.3 State and Territory management 102

7. TECHNIQUES TO MEASURE AND MANAGE IMPACTS AND ABUNDANCE 111 Summary 111 7.1 Estimating carp abundance 111 7.2 Measuring the impacts of carp on the environment 117 7.3 Population control techniques 121 7.4 Methods for impact reduction 130 7.5 Cost of control 134

8. STRATEGIC MANAGEMENT AT THE LOCAL AND REGIONAL LEVEL 137 Summary 137 8.1 Introduction 138 8.2 Define the problem 138 8.3 Develop a management plan 139 8.4 Implementation 152 8.5 Monitoring and evaluation 152 8.6 Case studies 156

9. IMPLEMENTATION 167 Summary 167 9.1 National level 167 9.2 Government involvement 167 9.3 The regional role of extension services and catchment management 169 9.4 Group formation 169 9.5 Facilitating effective groups 170

vi Bureau of Rural Sciences 10. DEFICIENCIES IN KNOWLEDGE AND PRACTICE 175 Summary 175 10.1 Introduction 175 10.2 Populations, distribution and abundance 177 10.3 Economic impacts 178 10.4 Environmental impacts 178 10.5 Population control techniques 179 10.6 Management 182 REFERENCES 185 APPENDIX A Economic strategies for carp management 205 ABBREVIATIONS AND ACRONYMS 209 GLOSSARY 211 SCIENTIFIC NAMES 219 INDEX 225

FIGURES Figur e 1 Strategic approach to managing carp damage. 10 Figur e 2 Distribution of carp of all strains. 25 Figur e 3 Key features of carp anatomy. 34 Figur e 4 Pharyngeal teeth. 35 Figur e 5 Theoretical stock-recruitment relationship for fish populations. 43 Figur e 6 Relationship between carp recruitment and spawner abundance in New South Wales. 44 Figur e 7 Diagram of whole otolith. 45 Figur e 8 Average length and weight of carp at different ages in southern Australia. 46 Figur e 9 Predicted lengths for female and male carp at different ages from the lower Murray River. 46 Figur e 10 Results of a survey of habitats around the Paroo, Darling, Murrumbidgee and Murray Rivers. 47 Figur e 11 Decline of native fish species. 57 Figur e 12 Model of the major effects of carp on structural and process components of the aquatic environment. 82 Figur e 13 Effect of exposure time on the relationship between carp density and plant biomass remaining. 86 Figur e 14 Catches of carp and black bream in Gippsland Lakes, Victoria, from 1987–88 to 1997–98. 93 Figur e 15 Possible relationships between carp density and the damage they cause. 94 Figur e 16 Relationship between carp density and cost of removal. 94 Figur e 17 Stable catches of Australian bass by anglers in the Hawkesbury–Nepean River system. 113 Figur e 18 Diagram of gill nets, drum nets and seines used to catch carp. 114 Figur e 19 Carp catches and changes in fishing effort in New South Wales from 1947-48 to 1995-96. 115

Managing the Impacts of Carp vii Figur e 20 Diagram of vertical slot, Denil and rock-ramp fishways. 132 Figur e 21 Little Moe River, Victoria, undergoing restoration to natural conditions. 161 Figur e 22 Flow diagram of strategic direction to carp control. 168 Figur e 23 Marginal analysis graph. 206

TABLES Table 1 Species in the Cyprinidae family relevant to or discussed in text. 13 Table 2 Summary of diagnostic characters of the cyprinids in Australia and of crucian carp. 16 Table 3 Summary of known genetic strains of Cyprinus carpio introductions in Australia. 20 Table 4 The ratio of length to width of the large pharyngeal teeth in carp, goldfish and hybrids. 34 Table 5 Disease and parasite organisms isolated from carp worldwide, effects of clinical disease, and known susceptibility of Australian native fish. 49 Table 6 Examples of current carp research in Australia. 59 Table 7 Problems associated with carp by landholder and angler organisations in New South Wales. 63 Table 8 Summary of supporting evidence for suggested impacts of carp in aquatic habitats. 80 Table 9 Common perceptions and facts about carp in Australia. 81 Table 10 Problems, causes and potential solutions for carp marketing in Australia. 89 Table 11 A summary of strengths and weaknesses of carp from market analysis. 89 Table 12 Values of carp. 90 Table 13 Status of carp, responsible managing agencies and relevant legislation for carp management in Australia. 100 Table 14 Key pathways which can allow expansion of the range of carp in Australia. 142 Table 15 Decision analysis table for consideration of factors affecting the acceptability of control measures for managing carp populations. 151 Table 16 The role of government agencies and community groups in implementing projects to manage carp impacts. 171

BOXES Box 1 Case study of large carp harvesting operation: sustained control 96 Box 2 Commercial harvest as one-off damage control in Sewerage Ponds, Lindernow, East Gippsland Water 97 Box 3 Estimating carp abundance: single mark–recapture method 117 Box 4 Estimating carp abundance: sequential depletion method 118 Box 5 Before-After-Control-Impact (BACI) 119 Box 6 Differences between impact and recovery studies 119 Box 7 Risk management principles 141 Box 8 Economic frameworks 148 Box 9 Best practice management of carp in a confined wetland area 156 Box 10 Best practice management of a small upland stream 161 Box 11 Best practice national carp management 164

viii Bureau of Rural Sciences Acknowledgments

Special thanks to Patrick Driver, Jane Roberts • Fisheries Research and Development and Richard Tilzey who provided thorough Corporation reviews of drafts of the manuscript. We also acknowledge feedback from Angela • Fisheries WA Arthington, Jim Barrett, Alan Baxter, Mike • Land and Water Resources Research and Braysher, Keith Breheny, Alistair Brown, Development Corporation Stephen Davis, John Diggle, Bob Dimmack, Colin Easton, John Harris, Alison King, Mark • Murray–Darling Association Lintermans, Andrea Mayes, Alex McNee, Bob • Murray–Darling Basin Commission McDowall, Bill O'Connor, Grant Rawlin, Bob Seamark, Adrian Toovey and many other • National Carp Task Force individuals who provided advice on the • National Consultative Committee on wide-ranging aspects of this publication. Animal Welfare Thanks also go to Keith Bell for his willing assistance with updating information and • National Farmers’ Federation organising photos. • Native Fish Australia Several individuals from the Bureau of Rural • Northern Territory Fisheries Sciences deserve mention. Quentin Hart managed the overall publication production • NSW Fisheries process and assisted with editing, design and • Queensland Department of Primary print management. Lisa Curtin incorporated the numerous modifications to the final Industries drafts, assisted with copy editing, typeset the • Rural Industries Research and document and had major responsibility for Development Corporation final production. Dana Bradford helped collate earlier drafts of the manuscript. Kim • South Australian Department of Primary Tatnell redrew the figures and provided Industries and Resources extensive design and typesetting input. Brett • Standing Committee on Agriculture and Cullen contributed to the design process. Resource Management To ensure that the guidelines are widely • Standing Committee on Conservation accepted as the basis for carp management, the draft manuscript was circulated to the • Standing Committee on Fisheries and following organisations for comment: Aquaculture • Animals Australia • Tasmanian Inland Fisheries Commission • Australian Conservation Foundation • Vertebrate Pests Committee • Australian Veterinary Association • Victorian Department of Natural Resources and Environment. • Carp Control Coordinating Group • Commonwealth Department of We thank these groups and hope that this Agriculture, Fisheries and Forestry document will facilitate their involvement in more strategic management of carp impacts. • Cooperative Research Centre for Freshwater Ecology • CSIRO • Environment ACT • Environment Australia

Managing the Impacts of Carp ix

Summary

The introduced carp (Cyprinus carpio) is age. In developing these guidelines the widely distributed throughout south-eastern authors have used all such available informa- Australia with smaller populations in tion. In some instances where reliable infor- Western Australia and Tasmania. Carp now mation is not yet available, managers dominate fish communities throughout responsible for carp management will have much of their range particularly in the to make assumptions about carp impacts and Murray–Darling Basin. Carp have the poten- the efficacy and cost-effectiveness of control tial to spread through many more of techniques. Australia’s water systems and could become even more widespread throughout the coun- Carp intr oduction and spr ead in try. Australia Carp can damage aquatic plants and increase Carp are in the family Cyprinidae and origi- water turbidity. Their impacts on native fish nated in China. They successfully spread species and other aquatic fauna are not well throughout Asia and Europe and developed understood. Carp are also becoming a as an ornamental and aquaculture species. resource, and are fished commercially and to Carp are closely related to goldfish, although a lesser extent recreationally. the presence of two pairs of barbels on carp These guidelines are a comprehensive distinguishes them from goldfish. The first review of the history of carp in Australia, records of carp introductions in Australia their biology, the damage they cause, and come from Victoria in 1859 and New South past and current management. The views of Wales in 1865. These carp were released into water and fisheries managers, conservation- ponds and did not spread into the wild. ists, animal welfare groups, commercial and During the 1900s carp were released into the recreational fishers, Aboriginal peoples and wild but did not become widespread. The other interest groups were sought during the Australian spread of carp largely began after production of these guidelines. Techniques they were released into the Murray River and strategies for carp management are rec- near Mildura, Victoria, in 1964. These fish ommended and illustrated by case studies. came from carp bred at a fish farm at Deficiencies in knowledge, management Boolarra, Victoria. The spread of carp and legislation are identified. throughout the Murray–Darling Basin, coincided with widespread flooding in the early The guidelines have been prepared primarily 1970s, but carp were also introduced to new for State and Territory management agencies localities, possibly through their use as bait. as a basis on which to consult with water Carp are now the most abundant large fresh- managers and relevant interest groups and to water fish in the Murray–Darling Basin and prepare State, regional and local strategies are the dominant species in many fish com- for reducing the damage carp cause to the munities in south-eastern Australia. environment and industry. It is a technical document which provides the scientific basis for the National Management Strategy pro- Economic and envir onmental duced by the Carp Control Coordinating impacts Group (CCCG). Carp have the potential to cause major costs The purpose of these guidelines is to assist in for both private and public sectors by lower- developing cost-effective strategies to ing water quality and damaging aquatic habi- reduce carp damage. Ideally, such strategies tats. Although there are few costings for carp are based on reliable quantitative informa- impacts on industries, those that may be tion about the damage caused by carp, the affected include domestic and irrigation water cost of control measures, and the effect that supplies, agriculture, and commercial and implementing control has on reducing dam- recreational fisheries. Because carp are not

Managing the Impacts of Carp 1 popular for eating or angling, most anglers Biology and Ecology have a negative image of them. Angling is one of the most popular recreational activities in The biology and ecology of carp are two of Australia and the dominance of carp in many the major reasons for their success as a verte- fish communities has the potential to reduce brate pest in Australia. Carp have broad envi- angler participation, particularly where num- ronmental tolerances and thrive in habitats bers of preferred native fish species are also which are disturbed by human activities, low. This could cause substantial losses to such as where river flows are altered, nutri- fishing equipment suppliers and tourist indus- ents are enriched and streamside vegetation tries associated with recreational fishing. is cleared. Carp feed by filtering small particles from the water or by sieving food items Most perceptions of environmental damage by from the bottom sediments. Juvenile carp carp focus on their potential to damage wet- feed mainly on small planktonic animals, lands, reduce water quality and harm native smaller crustaceans and insect larvae. As fish populations. Although carp are often carp grow they gradually eat larger crus- regarded as having a harmful effect on aquatic taceans and aquatic insects, along with some habitats and native aquatic species, there is lit- plant material. tle information on the overall impact and the costs that may be incurred. There has been Female carp mature at 2–4 years and may some limited research both in Australia and produce more than one million eggs per overseas on the potential environmental year. Eggs are normally shed onto plant impacts of carp, but many of the impacts are material in spring to early summer. Females not clear because they can also be caused by may spawn several times in one season. other factors. There is clear evidence that carp Juvenile carp live in shallow floodplain habi- increase water turbidity and damage many tats and are more abundant where the densi- aquatic plants, especially those with soft stems ty of adult carp is low. Growth rates of carp and shallow roots, and some evidence that vary greatly between different regions, carp increase water nutrient concentrations. depending on temperature, food availability Such damage can threaten endangered and population density. species, alter ecological functions and affect Survival of carp appears to be density-depen- tourism and recreational values of otherwise dent. This means that although large num- scenic wetlands. Impacts on native fish fauna bers of juveniles are produced, only a small are less well documented, even though carp number of young survive. The implication of now dominate many freshwater fish commu- this for reducing carp populations is that the nities. Declines in native fish populations in size of the reproducing population will need many areas occurred prior to the introduction to be substantially reduced to have any of carp. Increases in carp populations were marked effect on population growth rates. probably facilitated by the already reduced native fish populations, as opposed to a com- Carp carry a number of disease organisms. monly held perception that carp caused these Some of these, such as the Asian fish tape- declines. worm (Bothriocephalus acheilognathi) now occur in Australia, and may pose a serious Resour ce value risk to native fish. In Europe, carp carry Spring Viraemia of Carp Virus (SVCV) Much of the commercial carp catch is used (Rhabdovirus carpio), which causes Spring for low price products such as crayfish and Viraemia of Carp disease. This disease caus- lobster bait and fertiliser. There is currently es high mortalities in cyprinids, but has not little human consumption of carp in Australia yet been detected in Australia. and value-added products are only pro- Carp can migrate at any time of year. Some duced on a small scale. Commercial harvest- tagged individuals have moved over 200 ing is only likely to contribute to the control kilometres in a few months. Large numbers of carp in certain localised areas and is of carp have been recorded moving unlikely to achieve wide-scale population upstream during periods with low flows and reductions. rising water temperatures.

2 Bureau of Rural Sciences Carp are not normally predators of other fish. Techniques to contr ol carp Small carp may be an important part of the diet of larger predators, such as Murray cod To date carp control has mainly consisted of (Maccullochella peelii peelii). Competition commercial harvesting or poisoning. Whilst between carp and native species is poorly these options may reduce carp numbers, understood. By growing quickly to a large and poisoning may occasionally eradicate size, and feeding at low levels of the food them from isolated areas, other options are chain, carp may act as an energy trap, prevent- being explored for more widespread con- ing transfer of energy to populations of other trol. Environmental rehabilitation is seen as large fish. The feeding activity and diet of carp a way of improving habitat quality to favour may be an important factor in forming algal native fish. By potentially increasing native blooms. fish numbers, particularly larger predators, predation pressure on carp will be Community attitudes and increased. The use of viral agents for biological control such as SVCV is considered expectations to be unreliable for technical, commercial, Most attitudes towards carp in Australia are conservation and logistic reasons. Some negative. Many farmers and water authorities sectors of the public have expressed con- believe carp cause extensive damage to cerns about the use of viral control agents. channel banks. Recreational fishers and con- Potential genetic manipulation approaches servationists perceive carp as a nuisance. to carp control need to be explored. These However, many conservationists, scientists techniques, together with harvesting, rely and people interested in native fish, includ- on an adequate understanding of the ing recreational and commercial fishers, dynamics of carp populations. This infor- believe that carp are often used as a scape- mation is currently not available. Potential goat and are blamed for environmental molecular approaches include immunocon- problems which have other causes. traception to reduce carp fertility and the introduction of a fatality gene to kill individ- Due largely to negative media reports por- uals at a later date. There are currently no traying carp as a major cause of environmen- biological or contraceptive control agents tal problems, there is overwhelming public suitable for use against carp and gene tech- opinion that action is needed to reduce carp nology is not yet at a stage where it can be numbers. Commercial harvesting is seen as used for carp control. one option. This is often proposed without consideration of the economic viability of commercial operators who generally only Development of a strategic receive a low price for carp. A common management appr oach opinion is that harvesting carp will at least In the past there has been no coordinated reduce their densities and at best ensure management of carp in Australia and carp establishment of a market that could main- control has been mainly undertaken by State tain carp numbers below a level where they agencies, predominantly fisheries agencies. are a problem. But some community group The formation of the National Carp Task representatives have expressed concern that Force, as a result of public interest and pres- establishing a carp harvesting industry might sure, has promoted a more coordinated interfere with the ultimate control of carp. approach and national focus on carp control. Some conservationists, recreational fishers The CCCG has recently been formed with and indigenous representatives also consider State, Territory and Commonwealth represen- that the choice of control options for carp tatives to coordinate carp control on a national needs more emphasis on the role for rehabil- basis. There is now a need to progress itation of catchments and riparian areas. towards more strategic and scientific management. Integrated management using a range of control techniques produces the best results, but a lack of reliable information on control

Managing the Impacts of Carp 3 costs is seen as a barrier to adoption of some carp damage on a local and regional level, techniques. This deficiency should be involving cooperative action by water man- addressed if best practice management is to be agers, government agencies, industry and widely adopted. community groups. Monitoring and evaluation — Monitoring What is the strategic management has two aspects. Operational monitoring appr oach? assesses the efficiency of the management strategy over time, particularly to determine The emphasis in these guidelines is on the whether it is being carried out in the most strategic management of carp and their habi- cost-effective manner. Performance monitor- tats to minimise the damage carp cause to ing gathers information to evaluate the effec- aquatic habitats and conservation values, not tiveness of the strategy in meeting the merely to kill carp. Carp need to be consid- desired long-term production or conserva- ered as one factor in a complex and chang- tion objectives. Both forms of monitoring ing system which includes highly variable can help determine if and how the manage- climate and river conditions, and environment strategy should be modified. When mental damage from other causes. adaptive experimental management has A strategic approach to the management of been implemented, such monitoring and carp involves four key components: evaluation will enable improved and more cost-effective carp management strategies to Defining the problem — The problem first be developed. needs to be defined in terms of the impacts of carp on valued resources, whether eco- The above approach has been adopted for nomic or environmental. The next step is to developing these national guidelines. The quantify these impacts which will usually information in these guidelines is designed require experimental assessment of the dam- to facilitate the development of strategies for age. managing carp at the local and regional level. Management plan — In developing a management plan, it is essential that clear objectives are established wherever practicable in The futur e terms of the desired production and conser- More information in some key areas is essen- vation outcomes sought, relative to the costs tial if the strategic approach to carp manage- of control. Options for carp management ment is to be developed further. Knowledge include preventing further spread, eradicat- of many aspects of carp ecology in Australia ing existing populations, sustained manage- is relatively limited. In particular, information ment, targeted management, one-off man- on the dynamics of carp populations and agement or no management. Where feasible, their driving forces in the Australian environ- it is desirable to develop an adaptive experiment is lacking. Such information is critical mental management approach, based upon to the successful application of most man- the techniques available for carp control. agement techniques. Further development is Economic frameworks need to be developed also required for many of the potential con- to assist managers to assess the relative value trol techniques, including environmental of alternative control strategies. Such frame- rehabilitation, which may have widespread works require: definition of the economic application. problem, data on relative costs and benefits Two of the basic weaknesses in being able to of different carp management strategies, an determine priorities for where to control understanding of why the actions of individ- carp in many areas of Australia are the lack ual managers may not lead to optimum lev- of objective, quantitative data on the impact els of carp control, and how such problems of carp on the environment and a means of can be addressed. determining the cost of this environmental Implementation — The most effective damage. approach is to coordinate management of

4 Bureau of Rural Sciences There are few reliable data on the costs of carp control. Water managers need better information on the types and extent of damage caused by carp and on control costs. This will enable a change in management philosophy from one focussed on killing more carp to one focussed on cost-efficiently reducing the damage caused by carp. Adoption of these national guidelines will require an improved understanding of the principles for managing carp as a vertebrate pest at various levels, ranging from water managers to policy makers and officers of State agencies. Currently, there are limited numbers of extension staff working on carp and few are trained in the principles of education, sociology or psychology, all key elements associated with facilitating a change in behaviour in individuals or groups.

Managing the Impacts of Carp 5

Intr oduction

These guidelines for managing carp The strategic approach to managing carp (Cyprinus carpio) are one in a series pre- involves four key components: defining the pared by the Bureau of Rural Sciences (BRS) problem, developing a management plan, in cooperation with the Vertebrate Pests implementation, and monitoring and evalua- Committee of the Standing Committee on tion. These steps are outlined in Figure 1 and Agriculture and Resource Management. This discussed in Chapter 8. volume in the series was produced under the agricultural component of the National Feral Defining the pr oblem Animal Control Program (NFACP), a Natural Heritage Trust initiative. Other guidelines in Carp are widely regarded as having harmful the series include: feral horses (Dobbie et al. effects on the environment although there is 1993), rabbits (Williams et al. 1995), foxes little objective, quantified information. There (Saunders et al. 1995), feral pigs (Choquenot are no estimates of the economic impacts of et al. 1996), feral goats (Parkes et al. 1996), carp in Australia and few estimates of their rodents (Caughley et al. 1998), and wild environmental impacts. Determining the dogs and dingoes (Fleming et al. in press). nature and extent of the economic or envi- The current publication is the first publica- ronmental threat caused by carp requires tion in the series which addresses an aquatic knowledge of their status and biology. Thus, vertebrate pest. Chapter 1 describes the history of their introduction, Chapter 2 their spread, distribution A companion volume, Managing Vertebrate and abundance, and Chapter 3 their biology Pests: Principles and Strategies (Braysher and ecology. 1993), explains the principles on which best practice pest animal management is based Public attitudes can strongly influence the and should be read in conjunction with the perception of carp as a resource or as a guidelines. An overview volume, Olsen’s problem, and these views are examined in (1998) Australia’s Pest Animals: New Chapter 4. Chapter 5 reviews the evidence Solutions to Old Problems, reviews the man- concerning the economic and environmental agement of pest animals in Australia and impacts of carp in Australia and also reviews promotes a more strategic approach for commercial use of carp. Past and current future management. The benefits of focusing management of carp and their legislative sta- on the damage caused by a pest and not the tus are reviewed in Chapter 6. The impacts pest itself are explained. Olsen (1998) also of carp can be assessed in several ways, and explains the need to take into account the these are reviewed in Chapter 7, together links between different feral animal species with the efficacy of techniques to reduce and other aspects of land and water manage- these impacts. ment, consistent with the holistic approach to land management advocated under the Management plan Ecologically Sustainable Development Strategy and Landcare principles. Several management options are identified and discussed in Chapter 8 including pre- The objective of the national guidelines is to venting further spread through precaution- assist a change in approach to carp manage- ary management, local eradication, strategic ment from ad hoc measures by individual sustained management, commercial harvest- interest groups and agencies to a strategic ing and no management. There are several management approach based on coopera- options for managing carp damage, includ- tive action. These guidelines will have suc- ing removal by harvesting or recreational ceeded in meeting this objective when the fishing, environmental rehabilitation, exclu- strategic approach they advocate is accepted sion and poisoning. Future options may and implemented by a significant number of include the use of viral control agents, agencies and stakeholder groups. molecular approaches such as chromosomal

Managing the Impacts of Carp 7 manipulation and gender manipulation or Program, the Endangered Species Program the introduction of inducible fatality genes and the National Strategy for the and biomanipulation through predator Conservation of Biological Diversity. State stockings. Biotechnology options may not and Territory governments are responsible however be readily available for use by the for providing the legislative and regulatory community and must undergo stringent trials framework as well as facilitating and imple- before being deemed acceptable. Ideally a menting management on private and public carp management strategy will aim to land. achieve the desired reduction in damage by Chapter 9 discusses the roles of local, the most cost-effective means consistent State/Territory and Commonwealth govern- with ecologically sustainable use of the man- ments and community groups in developing agement system. In many cases, lack of and implementing carp management plans knowledge may initially prevent identifica- and the role of extension services and group tion of the best strategy for carp manage- action for achieving effective carp management. An adaptive experimental approach, ment. however, where the manager evaluates the benefits of a management action and continually modifies it in the light of experience Monitoring and evaluation (that is, ‘learning by doing’) is often the best Monitoring is an essential component of the approach. This is particularly applicable to strategic management approach. It enables carp, where many aspects of their ecology managers to determine whether their manage- under Australian conditions are not well ment strategy needs to be modified. understood. Chapter 8 describes how such a Operational monitoring aims to assess the effi- management strategy can be developed. ciency of implementing the management strategy and to identify areas where efficiency can Implementation be improved. Chapter 7 reviews techniques for assessing the cost effectiveness of control. A national strategy for managing carp dam- Performance monitoring seeks to evaluate the age encourages local and regional level outcome of the management plan; that is, plans to be placed in a national context. This whether the goals set initially in terms of pro- involves all managers and others with a sig- duction or conservation outcomes are being nificant interest in carp management cooper- met. Methods of evaluating such outcomes are ating at an early stage in planning and imple- also described in Chapter 7. mentation. At the national level, such an approach The futur e requires that the various roles and responsibilities of government agencies, groups and A major impediment to effective carp man- individuals are taken into account and inte- agement is a lack of information. There is grated. The Commonwealth Government is still a great deal of uncertainty about what involved in pest animal management the impacts of carp are, which makes it diffi- through agencies such as: the cult to set priorities for managing areas and Murray–Darling Basin Commission; BRS and to determine appropriate levels for carp the National Office of Animal and Plant reduction. Despite the widely held belief that Health in Agriculture, Fisheries and Forestry habitat manipulation has the potential to – Australia; and the Biodiversity Group in improve the competitiveness of native fish Environment Australia. The Commonwealth relative to carp, this has yet to be proven on a Government’s responsibilities for pest ani- large scale. There also needs to be further mal management include: exotic disease investigation of aspects of carp biology and preparedness and management, protection ecology that offer a management target as of overseas trade interests, and managing the well as target-specific, cost-effective control threats that feral animals pose to such techniques. The population dynamics of a national initiatives as the National Landcare highly fecund species such as carp also need Program, the National Feral Animal Control to be considered carefully to determine the

8 Bureau of Rural Sciences potential of various control strategies to have • Ranking Areas for Action: a Guide for a long-term impact on carp density and Carp Management Groups — sets out a abundance. Chapter 10 highlights deficien- process for establishing and ranking cies in the current state of knowledge and carp management units to prioritise looks to the research and management resource allocation and provides a step- developments which are needed to improve by-step process to develop and imple- future management. ment a management plan.

The National Feral Animal Contr ol • Future Directions for Research into Carp — identifies key knowledge gaps Program and provides the basis for progressing NFACP is a Natural Heritage Trust program management-based carp research. which works with State, Territory and local governments to reduce damage caused by pest animals to agriculture and the environment. The agricultural component of NFACP is administered by BRS and the environmen- All dollar values have been converted to tal component by Environment Australia. 1999-2000 Australian dollars unless Under its component of NFACP, BRS is pro- otherwise stated in the text. ducing these national management guidelines for the major pest animal species of agricultural production and is also supporting projects to address the information, management and extension deficiencies the guidelines identify and to demonstrate the strategic management approaches they advocate.

Linkage to the Carp Contr ol Coor dinating Gr oup's National Management Strategy for Carp Contr ol The Carp Control Coordinating Group (CCCG) was formed by the Commonwealth Government in 1998 to provide national leadership and coordination in the development and implementation of carp management initiatives. CCCG has prepared a National Management Strategy for Carp Control (NMSCC) which provides a national framework for effectively managing carp in Australia. The BRS guidelines complement this document by providing a detailed discussion of the biological, economic and strategic management principles which should be taken into account in developing management and research strategies. Associated with the NMSCC, CCCG has prepared two documents to guide the prioritisation and implementation of carp management and research in Australia:

Managing the Impacts of Carp 9 Evaluation (Section 8.5) Monitoring and efficiency outcomes – economic and/or – environmental • assess control • compare over time • compare techniques • evaluation of (Section 8.4) Implementation – ownership district • group action • whole catchment/ • government role • monitoring regime ) (Section 8.3) management; management; management; and – sustained – targeted – one-off – no control Management Plan units strategies – precautionary management; • select management • performance criteria • allocate management • define objectives • management options (Section 8.2) impact – economic – environmental Problem definition Problem Strategic appraoch to managing carp damage (after Braysher 1993 • who has the problem • real or perceived • define harmful • measure impact • mapping Figur e 1:

10 Bureau of Rural Sciences 1. Taxonomy and history of intr oduction

Summary spread to Europe and North America. Fossil cyprinids also occur in Africa, India and Carp belong to the family Cyprinidae. The south-east Asia as these fish extended their species originated in China and spread range when land masses moved. No throughout Asia. They were introduced to cyprinids reached the Celebes, New Guinea Japan (Koi strain) and Europe where they or Australia because the ancient Gondwana were developed as both an ornamental landmass, which formed Australia and species and as an aquaculture species for Antarctica, separated from the other conti- food. Carp are not native in North America nents before cyprinids evolved. Being pri- or southern continents. Carp are closely marily a freshwater species, cyprinids were related to goldfish and the two species are unable to cross the sea (Berra 1981) (Section mainly distinguished by the presence of two 3.5.5). pairs of barbels on either side of the carp’s mouth. ‘Carp have been successfully In Australia, carp were first introduced to introduced outside their natural Victoria in 1859 and to New South Wales in distribution to both the tropics 1865. Although these early introductions and temperate regions.’ were intended to establish populations in the wild, these attempts failed and carp remained in ponds. Aquarium imports into China is the heartland of cyprinids with indi- Sydney in 1907 resulted in contained popu- vidual river basins having a diverse fauna lations at Prospect Reservoir and Taronga (up to 111 cyprinid species in the Xi River Zoo. During the 1900s carp were again basin). The central European rivers also have released into the wild into rivers of New large numbers of cyprinid species South Wales. These may have been an Asian (Banarescu and Coad 1991). strain of Koi carp as this strain persists in The largest subfamily, the Cyprininae (called some of the original mainland release sites carps), contains 33 genera, all of European in the Murrumbidgee Irrigation Area, and and Asian origin (Howes 1991). The at Pooncarie in New South Wales. Koi carp Cyprininae did not reach North America so it also now occur in Tasmania, the Australian is speculated that this subfamily evolved Capital Territory and Western Australia, after North America separated from Eurasia probably from releases of Koi carp from (Howes 1991). Many species in this subfami- ornamental collections. ly have the word carp in their common name The most successful and now widespread — for example, grass carp genetic strain of carp is known as the (Ctenopharyngodon idella), black carp Boolara strain, and although the source of (Mylopharyngodon piceus), mud carp these fish is not verified, they were probably (Cirrhinus molitorella) and common carp imported into Victoria from Europe and did (Cyprinus carpio) (Table 1). In this book, the not spread widely until after 1960. name ‘carp’ always refers to Cyprinus carpio (Table 1). The name ‘European carp’, commonly used 1.1 Family Cyprinidae in Australia, is a misnomer. The genus Cyprinus orginated in east Asia. Cyprinus The Cyprinidae is a diverse fish family with spread naturally through central and north- around 2000 species grouped into seven ern Eurasia from at least the Oligocene (24 subfamilies (Howes 1991; Nelson 1994; million years ago) with evidence from a fossil Helfman et al. 1997). The fossil record for Cyprinus in Siberia (Cavender 1991). In east cyprinids dates from the Eocene age (58–37 Asia Cyprinus now has about 13 species million years ago) in Asia, from where they

Managing the Impacts of Carp 11 including C. Carpio (Banarescu and Coad 1.2 Carp in Eur ope and Asia 1991). There are genetic differences between the strains of carp in China and Europe, At least 80 species of cyprinids are used as a despite their common Chinese ancestry fishery resource, and many species are now (Shearer and Mulley 1978), but carp from exploited as a protein resource around the both continents are recognised as belonging world. Cyprinids are important for commer- to the same species (Section 1.4). In their cial wild harvesting (Section 5.4) and subsis- natural range carp coexist with a range of tence and commercial aquaculture (Section other cyprinid species. Carp have been suc- 4.8.2), as a recreational fishing species cessfully introduced outside their natural dis- (Section 4.9.2) and in aquarium culture as tribution to both the tropics and temperate companion or show species (Section 1.3.2) regions (Howes 1991; Section 3.2) (Cowx and Welcomme 1998). In North America, native cyprinid species are impor- Goldfish (C. auratus) (subfamily Cyprininae) tant for environmental monitoring and have are closely related to carp and have also been high conservation value (Table 1). In Europe successfully introduced outside their natural and Asia, both wild caught and cultivated distribution including into Australia (Howes carp are extremely important as food for 1991). Crucian carp (Carassius carassius) human consumption (Table 1). originated in Euro–Siberia where the Family Cyprinidae is the most diverse (Banarescu ‘In Europe and Asia wild caught and Coad 1991). Crucian carp do not occur in Australia but have been confused with gold- and cultivated carp are extreme- fish (Section 1.3.2). The rosy barb (Puntius ly important as human food.’ conchonius) (subfamily Cyprininae) was reported in Queensland as having self-main- Carp are native to China and Eastern Europe taining populations in Norman Creek, an (Section 1.1), possibly as far west as the urban stream in Brisbane, from 1970 until Danube River. In China about 3000 years 1984 (McKay 1984) but the population has ago, carp were first taken from the wild and since died out (Brumley 1996). reared in ponds for human consumption (Li Other cyprinids that have been introduced and Moyle 1993). This was the first attempt at outside their natural range into Australia are a managed aquaculture fishery to maximise from different subfamilies. They are roach production for food in China. Silver carp (Rutilus rutilus) from the subfamily (Hypophthalmichthys molitirix), big headed Leuciscinae (Howes 1991) and tench (Tinca carp (Aristichthys nobilis), grass carp and tinca) from the subfamily Tincinae (Table 1 black carp were reared with carp as their dif- and Table 2). ferent feeding habits allowed maximum use of food resources (Table 1). Carp probably grow more slowly than many of these other species but reproduce easily (Lin and Peter 1991). This practice is called polyculture and it still occurs in much of Asia for food production (Lin and Peter 1991). Carp may only comprise a small proportion of the total biomass. The traditional method involved the removal of large individuals and continual restocking with new small fish of all species during summer and autumn. In the first century AD, carp gradually spread Wild goldfish which have reverted to their natural across Europe with the assistance of the olive-bronze colour are sometimes mistaken for carp, Romans, who would have found carp in the but can be easily distinguished by their lack of barbels. Source: A. Brumley, East Gippsland Institute of TAFE. Danube River at the western extent of their

12 Bureau of Rural Sciences Aquaculture for food (Asia: China, Indonesia); Commercial fishing for food and recreational fishers, aquaculture for food (Europe) Ornamenatal aquaculture, recreational fishers for food Ornamental aquaculture (Japan, world-wide) Coarse anglers, aquaculture, commercial fishing Coarse angling Ornamental aquaculture Ornamental aquaculture Aquaculture for food, polyculture (detritivore) Aquaculture (grass eater), control of aquatic weeds, (North America, New Zealand) 8). Europe, Siberia, China, Asia China to Japan Danube Basin, stocked in lakes in Poland China to Hong Kong Area/country of origin Human use China, Danube Basin Europe South-east Asia China Prussian carp Other common names and strains Koi, Japanese domesticated carp, fancy carp Golden carp, Crucian native carp Common carp; European carp, scaled carp, mirror king leather carp Bala ‘shark’ Koi carp Common name used in this book Goldfish Carp Crucian carp Rosy barb Redtail black ‘shark’ Mud carp Grass carp European barbel Species in the Cyprinidae family relevant to or discussed in text (after Howes 1991; Helfman et al. 1997; Cowx and Welcomme 199 Species in the Cyprinidae family relevant to or discussed in text (after Howes 1991; Helfman et al. 1997; Cowx and Welcomme (41 species) (130 species)

Table 1: Barbus barbus Barbus Puntius conchonius* Cirrhinus molitorella Scientific name Subfamily Cyprininae Cyprinus carpio* Carassius auratus* Carassius carassius Puntius Ctenopharyngodon idella

Managing the Impacts of Carp 13 14 Scientific name Common name Other common names and Area/country of origin Human use used in this book strains Mylopharyngodon piceus Black carp China Aquaculture for food, polyculture (bottom feeder)

Subfamily Cultrinae Parabramis pekinensis Bream China Aquaculture for food, polyculture (mid-water feeder) Subfamily Leucisinae Rutilus rutilus* Roach Europe Coarse angling, aquaculture, commercial fishing in eutrophic lakes Scardinius erythrophthalmus Rudd Europe Coarse angling

Phoxinus phoxinus Minnows Dace Europe Coarse angling

Leuciscus cephalus Chub Europe Coarse angling

Leuciscus leuciscus Dace Europe Coarse angling, commercial fishing

Abramis brama Bream English bream, bronze bream Europe Coarse angling, commercial fishing

Blicca bjoerkna White bream Silver bream Europe Commercial fishing Bureau ofRural Sciences Hypophthalmichthys molitrix Silver carp China Aquaculture for food, polyculture Aristichthys nobilis Big-headed carp China Aquaculture for food, polyculture, (plankton eater), commercial fishing, angling Angling, conservation as natural predator Conservation in natural environment Bait, aquaculture Conservation, environmental monitoring Coarse angling, commercial fishing Human use North America North Amercia Area/country of origin North America North America North America Europe and Eurasia Baltic, Black and Caspian Seas Europe Other common names and strains Common name used in this book Colarado squawfish Shiners Minnows Minnows Fat-headed minnows Gudgeons Chekhon Tench spp. spp. spp. Scientific name Subfamily Tincinae *Introduced fish in Australia Ptychocheilus lucius Notropis Phoxinus Pimephales Pimephales promelas Subfamily Gobioninae Gobio gobio Subfamily Alburninae Pelecus cultratus tinca* Tinca

Managing the Impacts of Carp 15 16 Table 2: Summary of diagnostic characters of cyprinids in Australia and of crucian carp* (derived from Scott and Crossman 1973; Hume et al. 1983a; Breheny 1996; Brumley 1996).

Species Colour Lateral line Anal Barbels 1st gill Total length scales fin arch raker (millimetres) Common name Scientific name rays count Subfamily Cyprininae Carp, also called Cyprinus carpio Wild and in aquaculture: bronze or olive- 33–40 (usually 5–6 2 pairs (4) 16–20 (27) Usually up to common carp, gold, lighter beneath 34–37) large 600, maximum European carp, scales or 1200 Koi carp Ornamental: bright colours orange, white, reduced black; sometimes mottled. number of scales

Mirror carp, Wild: orange or olive-bronze; brown to Leather carp black Goldfish, also Carassius auratus Wild: orange or olive-bronze; brown to 26–30 (34) 5–6 0 35–40 (43) Usually up called golden carp black. Aquarium: bright colours and to 200, orange; sometimes mottled. maximum 400

Crucian carp* Carassius carassius Olive-green to reddish-brown dorsal; 35–38 6–8 0 26–31 Usually up lighter ventrally. Possibly darker lateral spot to 200 near the tail. Subfamily Leuciscinae Roach Rutilus rutilus Black olive-green body; silvery scales with >40 10–11 0 short Usually up reddish ventral fins and dusky dorsal and to 200, caudal fins maximum 450 Subfamily Tincinae Bureau ofRuralSciences Tench Tinca tinca Olive-brown to dark grey dorsally and >60 up to 6–7 1 pair 12–15 long Usually up lighter ventrally; body sometimes greenish 90–100, (small) to 300, gold to golden tan (rarely yellow-orange). very small maximum 700

* Often confused with goldfish and have never been verified as being present in Australia range (Moyle 1984). Monks were the first 1.3 Intr oduction of cyprinids to Europeans to culture carp for food and they Australia allowed carp escapees to spread into the river systems. Carp were well established outside of their original range across Europe 1.3.1 Victoria by the 1200s and into England by the 1600s. Carp were imported to Victoria in 1859–1862 Wild carp are now caught in Europe for both (Anon 1862), 1872 and 1876 (Hume et. al recreation and food. Some European ethnic 1983a). The first record of an import was groups include carp as a traditional compo- from 1859–60 (McCoy 1862) but this record nent of their diet originating either from is noteworthy because of the carp’s lack of commercial catches or pond culture. Carp success at surviving in captivity. Despite this are sought by English anglers as ‘coarse’ fish, setback, importers persevered with import- as distinct from ‘game’ fish such as trout or ing carp. The next records of imports are by salmon (Salmonidae). In a recent National the Geelong and Western District Opinion Poll (1997) in the United Kingdom, Acclimatisation Society in 1872 and 1876 carp were voted the most popular fish for (Clements 1988) but if these fish were recreational fishing (P. Smith, University of released into the wild, they apparently did Liverpool, United Kingdom, pers. comm. not survive (Hume et al. 1983a). The only 1998.) When bream (Albamis brama) and other mention of carp imports is into roach were removed from the Drayton Melbourne. A tantalising paragraph in the Reservoir (United Kingdom) and it was London Times of 18 October 1859 records: restocked with carp, income from fishing ‘Captain McMeckan did land 2 1/2 dozen increased from less than $5500 per annum carp from England with the object of domes- without carp to $140 000 during the 1995–96 ticating them to Victoria. They are now in the fishing year with carp present (P. Smith, care of Mr Brown of Como.’ There are no University of Liverpool, United Kingdom, Victorian records of this introduction except pers. comm. 1998.) for a letter to the Argus in 1860 that five carp In Japan, carp have been domesticated for and seven goldfish had come by ship from centuries for display as a result of their Plymouth (Clements 1988). colour, beauty and longevity. The Ma-goi, or The importation of carp was probably fancy carp, referred to in a book dated because of the desire of some of the colonists 714 AD, was derived from Chinese carp and to imitate a European environment in was cultured in ponds and in holding cages Victoria. Between 1851 and 1861, Victoria was in lakes (Takeshita 1969). Festivals, artwork an expanding colony whose residents needed and kites often carry a carp symbol. to gain wealth from control of resources and Worldwide, the genetic strain is called Koi, wanted pleasure and recreation (Gillbank and in the past century many new Koi vari- 1996). New plants, animals and fish were eties have emerged. Koi breeding has needed to establish new resource-based become popular in many countries including industries and recreation activities. The Australia and the United States of America. Acclimatisation Society of Victoria (1861) Cross-breeding with European carp, includ- which was established from the short-lived ing mirror carp (Cyprinus carpio) and Zoological Society of Victoria (1857) aimed to leather carp (C. carpio) from Israel and offer salmon, trout, carp and other fish for Germany and Japanese Ma-goi, has pro- anglers (Gillbank 1980). The first Annual duced new varieties of the Koi strain, includ- Report of the Acclimatisation Society of ing Doitsu, which has both large-scale and Victoria included an address by Professor scaleless varieties. Frederick McCoy, Professor of Natural Sciences at Melbourne University, who said ‘English bream, dace, tench, loach, roach and carp we have already imported and we are stocking the Yan Yean with tench’ (Anon 1862). Perhaps the interpretation is that only

Managing the Impacts of Carp 17 tench were liberated while the other fish, all chased from a dealer six carp which he iden- cyprinids (Table 1), remained in ponds beside tified as mirror or king carp (Cyprinus car- the Yarra River in the Melbourne Botanical pio) which would have had large scales Gardens under the direction of Dr Ferdinand (Table 1). Stead stocked these in a race Mueller. There is evidence that ornamental between two trout ponds. In 1910, the Board carp persisted in ponds in Victoria including of Fisheries transferred the mirror carp to be the Melbourne Botanical Gardens (Clements with the others in the inlet pond above 1988). In an eradication program by the Prospect Reservoir. A confusion of names Victorian Government in 1962 (Section 2.1.1 began when some Fisheries Department and Section 6.3.1) many large coloured carp records called them crucian carp. Stead were killed in ponds of the Botanical Gardens (1929) maintained they were all C. carpio (Clements 1988). Carp did not colonise natu- and some fish were taken from the inlet ral water bodies in Victoria in the 1860s, while pond to ponds at Taronga Zoological Park, trout and tench did. Carp were not bred at Sydney. This is the first record of carp surviv- any established trout hatcheries. ing in culture in Australia. Stead suggested a correction to the name but this was not There are no further recorded attempts at undertaken, so that the name of crucian carp introduction until the 1960s (Section 2.1.1). persisted (Whitley 1955, 1974). 1.3.2 New South W ales Introduced fish taxa, with self-maintaining wild populations, listed by Weatherley and The first carp brought into Sydney may have Lake (1967) included crucian carp, goldfish been a different genetic strain or species to and carp as well as roach and tench. Tilzey carp found later in New South Wales. The (1980) said that wild goldfish colonies were New South Wales Acclimatisation Society common and considered their wild coloura- was established in November 1861. Golden tion (olive-bronze) probably caused wild carp (Carassius auratus) and Prussian carp goldfish populations to be misidentified as (C. carassius), which are mentioned in their crucian carp (Table 2). Records of fish in the fourth and fifth Annual Reports (Anon 1865; Australian Museum in Sydney and the Anon 1866), were bred in ponds at Victorian Museum in Melbourne indicate that Government House in Sydney and are likely such misidentifications were made in the to have been goldfish and carp of European field. In 1980 museum curators and consul- origin. The Prussian carp may also have tants in New South Wales, South Australia, been crucian carp (Table 1). Sir John Young, Queensland and Victoria stated that they had the Governor, distributed these fish to creeks never seen a specimen of crucian carp from and lagoons between Sydney and Botany in Australian waters (J. Paxton, Australian 1866 (Strahan 1991). The ‘council Museum, NSW; J. Glover, South Australian [Acclimatisation Society] hoped that they Museum; M. Gomon, Victorian Museum and would multiply very rapidly, and be an orna- H. Midgley, Queensland Museum, pers. mental fish for water reserves, as well as a comm. 1980). It is now recognised that cru- palatable article of diet’ (Anon. 1866; Strahan cian carp do not exist in Australia. 1991). The Sydney Aquarium Society was formed in 1.3.3 South Australia 1907 and imports of many introduced fish No records exist of carp in South Australia began. Stead (1929) suggested that names of before 1960. Goldfish were brought in from imported cyprinids of Europe and Asia were China and kept in ponds along the River often confused with South American fish. In Torrens on the edge of the Adelaide 1907, Stead purchased fish he identified as Botanical Gardens from 1887 to 1896 (Rix carp, despite their incorrect label and mix- 1978). Some goldfish may have escaped and ture with goldfish, from a dealer in George been introduced to reservoirs (Mitchell Street. Stead sent nine small carp to large 1979). trout ponds and an inlet pond above Prospect Reservoir. In 1908 Stead also pur-

18 Bureau of Rural Sciences 1.3.4 Wester n Australia 1.4 Genetic strains of carp in Between 1896 and 1907 the Western Australia Australian Acclimatisation Society intro- Using genetic techniques, Shearer and Mulley duced many species of freshwater fish (1978) found two strains of carp were proba- including eels (Anguillidae), Atlantic salmon bly present for a considerable time before carp (Salmo salar), perch, tench and carp, all of began their great expansion of range in New which failed to establish wild populations South Wales in 1964 (Section 2.1). These were (Lever 1992). The only fish that established the Prospect strain in Sydney and the Yanco into the wild was brown trout (S. trutta) strain, probably of Koi origin, in the Yanco from fry imported from hatcheries in Victoria region of the Murrumbidgee Irrigation Area (Le Souef 1890; Lever 1992). Since then, sev- (MIA). Neither strain became widespread but eral other species of freshwater fish have remained localised to those regions after been imported into and have established in which they were named (Table 3). Western Australia. These include redfin perch (Perca fluviatilis), rainbow trout Translocations or introductions of carp prob- (Oncorhynchus mykiss), tilapia ably occurred within the Murray–Darling (Oreochromis spp.), gambusia (Gambusia Basin in the 1940s and 1950s (Brown 1996). holbrooki), guppies (Poecilia reticulata), There is also a New South Wales Fisheries sword tails (Xiphophorus helleri), and carp. report of 1931 that the Aquarium Society of In terms of impacts, it is possible that gam- New South Wales introduced upwards busia and tilapia pose a greater threat to of 50 000 fish, including ‘gold carp’ from aquatic ecosystems in Western Australia than Singapore, presumably into closed waters of carp. New South Wales (Clements 1988). Weatherley and Lake (1967) described carp as rare in the Murray River and the upper 1.3.5 Tasmania Murrumbidgee River and in irrigation chan- Carp are reported to have been introduced to nels in the 1950s and 1960s. There are Tasmania in the mid-nineteenth century but records of low catches of carp in New South there is no evidence of any established popu- Wales commercial fisheries catches from lations from these introductions (Diggle and 1952. The genetic strain represented by this Jarvis 1998). Carp were found in several farm population was probably the Koi strain from dams in the north-west of Tasmania in 1974 the Yanco region as identified by Shearer (Figure 2) and these were thought to have and Mulley (1978). Koi are often found with established from Boolara stock (Chapter 4). wild colouration and could be confused with These fish were soon eradicated (Section other strains of carp (Table 2). 6.3.5). In 1980, carp were found in the Stowport area and again were successfully ‘There is little genetic variation eradicated. In 1995, carp were found in two among carp in south-eastern lakes in the central highlands, Lake Crescent Australia, with the Boolara and Lake Sorell and attempts are being made strain accounting for most carp to eradicate them (Section 2.2.8). in the Murray–Darling Basin.’ 1.3.6 Queensland By 1960, carp populations existed in Victoria No records exist of carp in Queensland before from the stocking of farm dams (Wharton 1960. Carp are found mostly in the south-east 1979) (Section 2.1.1). These carp, and carp of the State, including in the Albert, Brisbane, reported in Lake Hawthorn and the Murray Condamine, Logan and Moonie rivers River near Mildura, north-western Victoria, (National Carp Task force Carp Database: were said to have come from a Boolarra fish www.sunfish.org.au/recfish/NCTF/Carpdatabase.htm) farm in Gippsland, Victoria (Wharton 1979) (Section 2.1.1). These were later called the

Managing the Impacts of Carp 19 Table 3: Summary of known genetic strains of Cyprinus carpio introductions in Australia (using McCoy 1862; Stead 1929; Weatherley and Lake 1967; Shearer and Mulley 1978; Breheny 1996 and Davis et al. 1999b).

Strains Date of introduction Locality of Current distribution to water introduction

Unknown 1859–1876 Melbourne, Victoria Not established

Prospect 1907 & 1910 Sydney, New South Restricted Wales

Yanco (Singapore, Possibly 1930s & 1940s Murrumbidgee Irrigation Restricted Koi) Area, New South Wales Now in Pooncarie and Narrandera regions in New South Wales

Boolara 1962 Gippsland and Lake Became established in Hawthorn, Victoria Murray–Darling Basin to be a dominant species Widespread throughout most of south-eastern Australia

Koi 1976 Lake Burley Griffin, Uncertain; in all urban Australian Capital lakes but could also be Territory in Murrumbidgee System

Koi 1990s Lake Crescent, Tasmania Restricted

Koi 1990s Coastal rivers near Restricted Perth, Western Australia

Boolara strain (Table 3) by Shearer and these, Yanco carp from the MIA were the Mulley (1978). most distinct genetically and it was suggested these had Asian ancestry. Because the Shearer and Mulley (1978) examined carp Prospect and Boolara strains differed at one from three main areas: weirs and dams locus only, Shearer and Mulley (1978) throughout the Murray–Darling Basin, the thought they were likely to be from similar MIA and Prospect Reservoir. They recognised European ancestry. three distinct strains of carp based on external colouration and electrophoresis protein Genetic strains of carp in the Murray–Darling analysis, which they referred to as the Basin were examined by Davis et al. (1999b) Boolara, Yanco and Prospect strains. Of

20 Bureau of Rural Sciences using newer techniques. By this time carp populations were established and interbred. In addition to the Yanco strain, Davis et al. (1999b) identified a wild Koi strain which accounted for 100% of the population at a Koi aquaculture facility in Bringelly near Sydney, 71% of carp in Lake Burley Griffin in the Australian Capital Territory, and 95% in Lake Crescent in Tasmania. The Yanco strain remains as a minor variant and only occurs at Narrandera (21% of carp sampled) and in the Darling River at Pooncarie (15%), (Davis et al. 1999b). The Koi strain, imported directly from Asia, has not become widespread in south-eastern Australia (Davis et al. 1999b). Koi carp are now found in Western Australia and were imported in the 1990s (Breheny 1996; Table 3; Section 2.2.6). There is little genetic variation among carp in south-eastern Australia (Davis et al. 1999b) (Table 3). The Boolara strain is now found throughout the region and accounts for all carp in sites selected by Davis et al. (1999b) in the MurrayDarling Basin except for the few sites with Yanco or Koi strains. Davis et al. (1999b) did not collect carp from Prospect Reservoir where the Prospect strain identified by Shearer and Mulley (1978) may still be present. There is some evidence that there are genetic differences between the carp in the Logan and Albert rivers in south- east Queensland and the Boolara strain common in the Murray–Darling Basin. This may suggest they originated from a separate introduction (B. Pollock, Department of Primary Industries, Queensland, pers. comm. 1999). It is likely that the successful strain of carp in Australia, held by Boolarra Fish Farms Proprietary Limited in 1960 (Section 2.1.1), was imported from Europe although this is not documented (Brown 1996). The carp were initially thought to be derived from those translocated during the 1900s (Shearer and Mulley 1978).

Managing the Impacts of Carp 21

2. Dispersal, distribution and abundance

Summary ing wetland and riverine habitats of waterfowl and fish followed news of the spread of carp. The wide-scale spread of carp in Australia This probably resulted in the publication of began after they were released into the results from a visit to North America by the Murray River near Mildura, Victoria, in Victorian Director of Fisheries, and the result- 1964. These fish originated from carp bred at ing Report of the State Development a fish farm at Boolarra, in Gippsland, Committee (1961–62) (State Development Victoria. Floods accelerated the spread of Committee 1962) (Section 6.3.1). The Director carp throughout the Murray–Darling Basin, of Fisheries had heard evidence of destruction but carp were also introduced to new locali- of wetland areas and increasing muddiness of ties, possibly through the use of small carp as water where carp were present. This aroused bait. Carp are present in both natural and concern for the future of Australian waters disturbed habitats and survive throughout even though many native fish species had the Murray–Darling Basin, which has been already declined due to other factors (Section altered extensively by European settlement. 3.5.5). The director lobbied to prohibit intro- Forms of disturbance in aquatic habitats duction of exotic food fish, including carp, to include sedimentation, cleared banks, chan- Australia, because of problems encountered nel alteration, and increased nutrients due to in North America. An inquiry was held into land clearing and use. The most noteworthy possible effects of carp, and after twelve habitat change is river flow alteration caused months the Report of the State Development by dams and weirs and diversion of water Committee, Victoria (1961–62) made 24 con- from rivers, which has impeded the spawn- clusions that included: ing, recruitment and migration of native fish and created habitats in which carp survive ‘All European Carp and its domesticated well. The overall effect of these disturbances is forms now or in future present in Victoria a loss of physical habitat for native fish. Carp whether occurring in private waters or in are the most abundant large freshwater fish waters defined under the Fisheries Act 1958 in the inland Murray–Darling Basin. should be destroyed.’ ‘There is a need for legislative action to enable the prohibition of European Carp cul- 2.1 Factors contributing to the ture in Victoria.’ spr ead of carp ‘There is a need for legislative action to authorise the destruction of European Carp 2.1.1 Hatchery pr oduction in and its domesticated forms in Victoria.’ Victoria in 1960 Carp were subsequently regarded as a pest A carp (Cyprinus carpio) aquaculture venture and declared noxious. The Victorian was initiated by Boolarra Fish Farms Department of Fisheries and Wildlife under- Proprietary Limited at Boolarra in Gippsland, took an eradication program to kill all carp in Victoria in the late 1950s. Hatchery-produced farm dams with poisons (Section 6.3.1). carp survived in the wild in Victoria when In 1964 and 1965 carp were reported in Lake they were stocked into a fire service reservoir Hawthorn near Mildura. This release origi- in Morwell, south-eastern Victoria in 1960. In nated from the Boolarra farm (Pribble 1979) the two years following establishment of carp and gave carp access to the Murray River. populations in Morwell and distribution to Over the next five years carp were reported other areas of Victoria, carp became estab- in the Murray–Darling system radiating from lished in the Yallourn Storage Dam and in the central Mildura area. The distribution of 1962 spread to the La Trobe River and then to carp in 1970 is shown in Figure 2. These Lake Wellington. Public fear of carp disturb- were carp of Boolara strain (Section 1.4).

Managing the Impacts of Carp 23 2.1.2 Floods and dr oughts Not only were carp widespread by 1998 (Figure 2), but their relative abundance was Large floods in 1974 and 1975 in the high compared to other species. Carp and Murray–Darling Basin facilitated the rapid goldfish (Carassius auratus) were more spread of carp throughout that river system. abundant than any native fish in surveys of Records to 1976–77 show a spread of carp to northern Victorian waters during 1979–83 the mouth of the Murray River and upstream (Brumley et al. 1987). into the Darling River (Figure 2). Numbers increased throughout the Murray–Darling There appears to be little movement of carp River system. By 1976, the Fisheries out of wetlands back into main channels in Department was concerned that carp had times of drought. During drought years become an established species in Victoria many carp often become trapped and die, (Wharton 1979). revealing the large biomass densities and successful population growth in wet years. ‘Floods give carp the ability to This first occurred in the mid 1970s and has spread rapidly through a river, occurred in subsequent droughts (Brown including anabranches, still 1996; Hoy 1998; Barlow 1998a; Johnson waters and billabongs where 1998; Barlow 1998b; Wright 1998). they can become trapped when water levels recede.’

During 1993 extensive flooding also occurred in much of the Murray–Darling Basin. Although carp were already common in the Paroo, Murray and Murrumbidgee Rivers in the northern and eastern areas of the Basin, numbers caught rose dramatically during these floods (Gehrke et al. 1995). By 1998 carp were widespread throughout the Murray–Darling Basin (Figure 2). Koehn and Nicol (1998) found carp regularly moving through rivers both upstream and downstream under normal river conditions. Floods Drought conditions sometimes reveal the extremely give carp the ability to spread rapidly high biomasses of carp that have established in some through a river, including anabranches, still inland waterways. Source: A. Brumley, East Gippsland waters and billabongs where they can Institute of TAFE. become trapped when water levels recede. 2.1.3 Deliberate intr oductions and In the Queensland portion of the use as live bait Murray–Darling Basin, carp are present in all of the major river systems (Paroo, Warrego, Small carp have been regularly used as bait Condamine–Balonne and Macintyre). Their throughout the Murray–Darling Basin, partic- spread in the Condamine–Balonne appears ularly for catching larger species such as to have been slowed by the presence of Murray cod (Macullochella peelii peelii). numerous weirs, and their 1998 range Carp now occur above the large impound- (Figure 2) appears to be limited to weirs in ments such as Hume, Burrinjuck and many the vicinity of Millmerran (D. Moffat, other smaller dams in New South Wales. Queensland Department of Natural Carp have appeared in the Wimmera River Resources, pers. comm. 1998). The spread of system of Victoria, in the Shoalhaven River in carp upstream in the Condamine–Balonne is New South Wales and recently in Lakes expected to continue with each successive Crescent and Sorell in Tasmania (Brumley flood and resulting weir drown-out (D. 1996; Sanger and Koehn 1997). These intro- Moffat, Queensland Department of Natural ductions are likely to be a result of anglers Resources, pers. comm. 1998). using live carp for bait. Carp in Lake

24 Bureau of Rural Sciences Distribution of carp

1970

1977

1998

Lake Eyre Millmerran

Leigh Creek Dam

er Riv g lin ar Pilby Creek D Case Study Section 8.6.1 hlan River Lac River

ADELAIDE Macq Prospect Reservoir uarie Ri ver SYDNEY Onkaparinga R Murray Shoalhaven River G o Lake Alexandrina u l b u rn R MELBOURNE

Gippsland Lakes

Little Moe River Case Study Section 8.6.2

Lake Sorrell

Lake Crescent

HOBART

Figur e 2: Distribution of all carp strains, predominantly Boolara strain (Koi in Tasmania and Western Australia) in 1970, 1977 and 1988.

Managing the Impacts of Carp 25 carp. Education of anglers about the potential harm caused by carp is needed to minimise these risks. To assist in controlling the spread of carp, the use of live fish as bait is illegal in Victoria and New South Wales.

‘There is increasing concern that some coarse anglers might deliberately introduce carp to Regulation of river systems by dams and weirs has had new areas.’ a detrimental effect on the life cycle of some native fish species but is likely to have favoured carp in some areas. Source: A. Toovey, NSW Fisheries. Deliberate release of unwanted aquarium fish is often the cause of introductions of exotic fish to waters and this is the likely Crescent have been identified as Koi carp (Section 1.4; Davis et al. 1999b) which may source of goldfish where they occur in the indicate an origin from mainland Koi. They wild in Australia (McKay 1984; Brumley may have been taken to Tasmanian lakes for 1991). The presence of goldfish in the wild is use as bait in the trout fishery. The presence of concern because goldfish can hybridise of carp in Leigh Creek Dam in the Lake Eyre with Yanco and Boolara strains of carp drainage basin and the Onkaparinga River in (Shearer and Mulley 1978; Hume et al. South Australia (Figure 2) was attributed to 1983a) (Section 3.1). These hybrids are likely either anglers or a deliberate release (Brown to be fertile. 1996). The number of coastal systems with carp has increased along the New South Wales coast (Figure 2) largely as a result of use of carp for bait and deliberate introduc- 2.1.4 Habitat disturbance tions (J. Harris, NSW Fisheries, pers. comm. The invasion by carp has been associated 1995). It is thought that carp were first intro- with habitat disturbance caused by develop- duced into the ACT as a contaminant of ment and environmental exploitation of releases of native fish (M. Lintermans, Australian waters during post-European set- Environment ACT, pers. comm. 1999). Such tlement (Williams 1967; Cadwallader 1978; contamination of stocks may have occurred Lake 1980). This disturbance has favoured elsewhere, and this would explain why carp invasion by carp (Section 3.2) and made now occur in many large impoundments in many habitats less suitable for native fish New South Wales. To avoid this problem, species. The following types of disturbance many hatcheries have installed devices and of inland waters occurred concurrently with, implemented quality control procedures to or preceded, the invasion of carp. prevent carp and other unwanted species and disease organisms being accidentally Development of water resources stocked with live fish. There is increasing concern among those Dams, weirs and large reservoirs with artifi- responsible for managing carp that some cial canals were built to control water for coarse anglers might deliberately introduce agriculture, flood mitigation and hydroelec- carp to new areas to establish new carp fish- tricity. Construction began in the 1850s and eries. Carp have established populations in involved many large engineering feats from isolated locations in recent years, presum- the 1890s to the 1950s. In rural districts, ably as a result of accidental releases of small extensive networks of irrigation channels carp used for live bait, or following deliber- were built to distribute water to farms. By ate releases by people wanting to spread 1966, dams and weirs in irrigation and water

26 Bureau of Rural Sciences trust schemes covered an area of 2.4 million Wetlands drainage and catchment hectares (Swan 1974). In other reaches not clearing supplied by dams, irrigation companies pump vast quantities of water direct from the The Murray–Darling Basin was settled rapidly river. This development and exploitation of after the crossing by Hume and Hovell in water resources has affected native fish by 1824 and the journey of Sturt in 1829. altering the frequency, duration, timing and Squatters spread along the river system with size of low and high flow events, changing sheep and cattle and river traffic increased the natural seasonal flow cycle, providing (Buxton 1974), and by 1850 most river cold water from low level off-takes, and pro- frontage plots were settled. There was little ducing barriers to movements and migration attempt at resource management, with heavy (Cadwallader 1977; Harris 1984; Koehn and stocking, land clearing and farming and O’Connor 1990a; Gehrke et al. 1995). forestry practices causing bank erosion, silta- Another effect of weirs is an increase in the tion and changed river productivity (Buxton extent of still-water habitats with macro- 1974). Draining and levee construction phytes providing more spawning habitat for around floodplain areas contributed to heav- introduced fish, including redfin perch ier flows within rivers and the deepening of (Perca fluviatilis) and tench (Tinca tinca) rivers with unstable beds and incised chan- (Cadwallader 1977) and probably carp. The nels. salinity of the Murray River between Riparian vegetation is vital for river habitats. Yarrawonga in New South Wales and Koehn (1993) highlighted the value of native Morgan in South Australia has increased at bankside, or riparian vegetation to provide: least 10-fold between 1878 and 1986 (Close instream organic native fish habitat, organic 1990) because of increasing irrigation devel- matter for aquatic invertebrates, terrestrial opment. Carp are more resilient to salinity insects for fish food, roots preventing bank than many native Australian fish species erosion, buffer strips for catchment run off, (Section 3.2.2). and shading of the stream. Where riparian vegetation has been cleared, river banks ‘Habitat disturbance has have been scoured and collapsed, causing favoured invasion by carp and changes in river habitats and fish communi- made many habitats less suitable ties (Growns et al. 1998). for native fish species.’ Sedimentation Many wetlands have become more perma- In the 1860s, extensive land clearance was nent because of artificial overbank flows undertaken in Victoria to provide timber for from irrigation. These habitats not only lose mining operations and steam machinery. their natural drying cycles but also provide This resulted in erosion which carried large permanent refuges and ideal spawning sites amounts of sediment into nearby rivers. for carp (Fletcher et al. 1985). The variability Land clearance for agriculture continued into of billabongs is diminished over time with- this century, further contributing to sedimen- out the flooding and drying cycle, resulting tation in rivers. Sedimentation has also in a loss of habitat diversity. Other factors occurred from dam and road construction, may contribute to deterioration of pristine unmade roads and cattle access points. Fine billabongs, including intrusion of cattle sediments increase the turbidity of the water, (Roberts 1997) and nutrient run off. The cover plants and rocky habitats and smother chemical nature of billabongs is variable and eggs, spawning sites, substrates and inverte- depends on the surrounding land. brate food sources for fish (Koehn and Sedimentation and subsequent turbidity can O’Connor 1990a). vary with the immediate soil types (King et al. 1997) and the hydrological patterns of the region (Fletcher et al. 1985). High turbidity reduces light penetration into the water, limiting growth of aquatic plants.

Managing the Impacts of Carp 27 Snag and habitat removal and nitrogen availability are generally low in Australian waters, so that catchment clearing, Where rivers have been thought of simply as application of fertilisers (especially super- distribution channels or navigable water phosphate), irrigation, effluent from dairy bodies, many physical modifications such as farms, sewage and storm water with deter- straightening, desnagging and channel clear- gents have caused elevated nutrient levels in ing were done in the name of ‘river improve- many rivers. Stock access to streams also ment’. In many rivers the removal of snags, leads to elevated nutrients, and increased or large woody debris, continued into the bacterial and viral counts as a result of faecal 1980s in the belief that the debris contributed contamination. Cold water pollution from to flooding and bank erosion and restricted low-level dam outlets often prevents spawn- the delivery of water downstream. Unless, ing for many native warm water fish species however, the channel is fully blocked this (Koehn and O’Connor 1990a). practice has been discontinued. Removal of large woody debris has caused large-scale Introduction of exotic fish species loss of habitat for fish and invertebrates and has often accelerated erosion. Snags are the Introduced tench and redfin perch were main structural habitat component in low- already widespread when carp populations land rivers and are used as habitat sites for expanded in the Murray–Darling Basin. refuge, territories, spawning and sources of Brown trout (Salmo trutta) were also well food (invertebrates) by native fish (Koehn established in upland streams above 300 and O’Connor 1990a,1990b). The removal of metres. Redfin perch and trout (Salmonidae) riparian vegetation contributed to the loss of competed with native fish and preyed upon input of new material. some species. Native river blackfish (Gadopsis marmoratus) and native moun- Timber harvesting tain galaxias (Galaxias olidus) suffered direct negative effects of predation and com- Campbell and Doeg (1989) demonstrated petition from introduced trout resulting in that logging operations increased the sedi- their decline (Jackson and Williams 1980; ment and nutrient load, and altered dis- Fletcher 1986). There were large catches of charge of streams in forested catchments. redfin perch in the Murray River from More light is able to penetrate streams after 1919–49 which alternated with catches of logging of surrounding vegetation, accelerat- native Murray River fish, hinting at competi- ing growth of algae or aquatic plants and tion and predation relationships. changing the composition of invertebrate fauna. Natural shading prevents high water Introduced plants temperatures harmful to native plants and animals, and creates patchy light as habitat Introduced plants disturb stream habitats. for predators and prey and is often lost by Willows (Salix spp.), with fine spreading timber harvesting. roots, can alter the course of the river and use excessive water. Poplars (Populus spp.) Pollution have shallow roots and can fall. The leaves of these species are not as suitable for aquat- Pollutants such as sewage, pesticides, indus- ic invertebrates as the leaves of native vege- trial effluent and saline waters have been tation. Terrestrial insects living in willows known to cause fish kills and lethal residues. also differ from the insects that live in native Nutrients washed in from agricultural and trees (Campbell 1993) and the seasonality of urban areas have contributed to algal blooms leaf fall also differs, with willows being and reduced water oxygen concentrations. deciduous while native trees shed leaves Eutrophication is the increase in nutrients throughout the year. Willow root masses trap causing excessive growth of only a few toler- silt, and invertebrates that occur in silt, such ant taxa, for example, bluegreen algae as chironomids and oligochates, are (Cyanobacteria), larvae of midges favoured by carp (Hume et al. 1983a). Many (Chironomidae) and worms. Phosphorus of these changes are detrimental to native

28 Bureau of Rural Sciences fish whereas carp often occur in large num- temperatures, replanting of riparian fringing bers among dense stands of willows (Gehrke vegetation (Koehn and O’Connor 1990a) and and Harris 1996). other catchment rehabilitation programs.

Overfishing 2.2 Distribution and abundance The decline of native fish could have been affected in part by the exploitation of stocks by commercial and recreational fishing. 2.2.1 General distribution Large numbers of Murray cod and golden In south-eastern Australia carp have become perch (Macquaria ambigua) were harvested established in many rivers (Figure 2) and (Cadwallader 1977). In New South Wales their associated aquatic habitats including native fish catches declined, after a peak in anabranches, billabongs and backwaters. 1918, to a point in the 1930s where commer- Floodplain wetlands and billabongs are cial fishing was unprofitable for large-scale important habitats in the life cycle of carp. operations (Rowland 1989). Carp are dominant and widespread in billabongs in both dry and wet years (Walker Management of disturbed habitats and Hillman 1977; Fletcher et al. 1985; Gehrke et al. 1995; King et al. 1997). Juvenile Catchment management aimed at addressing carp are often extremely abundant in flood- these problems has occurred since the 1940s plain wetlands after inundation (Gehrke et but progress has been slow. It was not until al. 1995; Gehrke et al. 1999b). the 1980s that the Victorian Government concluded that there was a problem with the Under natural conditions many billabongs State’s rivers and recognised the full extent with an assemblage of littoral vegetation and of the impact of past catchment practices macroinvertebrates dry up and recycle nutri- (Anon 1983). ents from the decomposing plants. During the drying phase carp may become concen- ‘Carp have benefited from the trated and can be observed in great num- decline of native fish populations bers. These fish die if the wetland dries completely (Section 2.1.2). For this reason, the in an altered habitat.’ occurrence of carp in temporary wetlands can be highly sporadic and is strongly linked Management decisions followed the accurate to the wetting and drying cycle (Gehrke et al. environmental assessment that occurred in 1999b). the 1980s in Victoria (Mitchell 1990). Current programs include the National Monitoring 2.2.2 V ictoria River Health Initiative, the New South Wales River Survey, and the New South Wales Rivers Water Reform process and Integrated Monitoring of Environmental Flows. In the Victorian Carp Program (1979-82), Queensland water resources are currently backwaters and anabranches in the subjected to assessment, accompanied by a Goulburn River catchment were selected as Water Allocation Management Process, to study sites for their dominance by carp document the attributes of aquatic habitats. (Hume et al. 1983a). Further sampling in Victoria to find native fish species in 16 tribu- Carp have benefited from the decline of taries of the Murray River found carp in 75% native fish populations in an altered habitat. of sites, which was much more than any The environmental changes that have native species (Brumley et al. 1987). Sites occurred in over 200 years since European that did not have carp were the lower reach- settlement cannot be reversed, although es of the Wimmera River in western Victoria, some of the effects may be reduced by upper reaches of Seven Creeks, King River implementing environmental flow regimes and Cudgewa Creek in the north-west. (Gehrke 1997b), restoring habitats and water

Managing the Impacts of Carp 29 By 1998 carp were recorded in all but 7 of In a study of the distribution of all fish in the the 39 Victorian river basins and dominated Seven Creeks system of the Goulburn the fish fauna in urban waters in Melbourne. Catchment in central Victoria, carp were only Records of carp from the Otway coast river found at lower elevations (Cadwallader basin have not been substantiated. Carp 1979), but this finding may be attributable to were also reported from the Snowy River the barriers imposed by series of rocky area (Malcolm 1971) but these may have waterfalls. been goldfish. The only catchments without carp in Victoria are now the far-eastern Estaurine systems and coastal Snowy and east Gippsland catchments (T. lakes Raadik, Freshwater Ecology, Department of Natural Resources and Environment, Carp released into the La Trobe River, Victoria, pers. comm. 1998) (Figure 2). The Gippsland, Victoria, soon spread down- far south-west of Victoria may also not have stream to Lake Wellington and the Gippsland carp but there has been a recent uncon- lakes. These lakes were once freshwater but firmed report of carp near the Rocklands have increased in salinity since an artificial reservoir (T. Raadik, Freshwater Ecology, ocean opening was made in 1890s. Carp per- Department of Natural Resources and sist in salinities of at least 10–18 parts per Environment, Victoria, pers. comm. 1998). thousand but move up the rivers into fresher Further spread to the upper Glenelg River water at higher salinities (A. Brumley, East catchment would be of concern. Gippsland Institute of TAFE, Victoria, unpublished data, 1998). Impoundments and artificial lakes 2.2.3 New South W ales The majority of lakes are constructed impoundments. Myers (1981) classified 407 Rivers Victorian inland waterbodies ranging from less than 1000 megalitres capacity, to four In New South Wales, carp occur throughout dams of 1–5 million megalitres capacity the slopes and lowland tributaries of the (Dartmouth, Eildon, Hume and Thompson). Murray–Darling system at elevations of below 700 metres (Gehrke et al. 1995; Harris None of the larger still water bodies in and Gehrke 1997). In coastal rivers, carp Victoria are natural. Carp occur in most of have been recorded from rivers near major these modified lakes and waterbodies centres of human populations in the (Brumley et al. 1987; T. Raadik Freshwater Shoalhaven, Hawkesbury–Nepean and Ecology, Department of Natural Resources Hunter catchments (Harris and Gehrke and Environment, Victoria, pers. comm. 1997). 1998; Gehrke et al. 1999b). The only lakes with carp are the Gippsland lakes and many Impoundments and artificial lakes deflation basins with intermittent river connections. Some dams, such as the Menindee Lakes and Carp are also comon in farm dams and irriga- Lake Victoria in New South Wales, were natu- tion channels in Victoria, but there are no ral lakes that have now been modified by the estimates of their overall abundance in these water industries. These lakes contain carp. waterbodies. Some water storages contain large populations of carp. In December 1997, a cyanobac- High Elevations terial bloom in Wingecarribee Reservoir in New South Wales was treated with copper Carp can survive in high elevations where sulphate. This caused a large fish kill includ- they occur in lakes and impoundments. ing an estimated 15 000 carp weighing However carp may be restricted to lower ele- approximately 26 tonnes which were vations within natural tributaries. removed from the water. No estimates are available of the number of carp left in the lake (P. Gehrke, NSW Fisheries, unpublished data, 1998).

30 Bureau of Rural Sciences Carp are also common in farm dams and irri- goldfish (R. Mackay, Queensland Museum, gation channels in New South Wales, but pers. comm. 1994). Carp have recently been there are no estimates of their overall abun- reported in the Albert River catchment in dance in these waterbodies. south-east Queensland, where their numbers and distribution have steadily increased dur- High Elevations ing the 1990s (M. Kennard, Griffith University, Queensland, unpublished data, In a survey of New South Wales rivers, carp 1999) (Figure 2). were rare at altitudes greater than 500 metres above sea level and were not recorded high- The spread of carp in the Severn River, the er than 600 metres above sea level (Driver et main tributary of the Macintyre River in al. 1997) (Section 3.2.1). Queensland, appears to be restricted by a natural barrier of a large intermittent water- fall downstream of Stanthorpe (D. Moffat, 2.2.4 South Australia Queensland Department of Natural Rivers Resources, pers. comm. 1998). Carp are not in the headwaters of the Warrego River in In South Australia, carp occur in the Murray Queensland but this is probably an effect of River down to the barrages at the river mouth. intermittent water availability. There are also reports of carp in other rivers and streams, mostly in the south-east of the 2.2.6 W ester n Australia State, including in the Finniss, Gawler, Light, Marne, Torrens and Wakefield Rivers Rivers (National Carp Task Force, Carp Database: www.sunfish.org.au/recfish/NCTF/Carpdatabase.htm). Carp were said to occur in Western Australia in 1947 and 1957 in swamps and the main Estaurine systems and coastal stream of the Swan River (Breheny 1996). Carp were reported to have spread widely lakes (Twyford 1991), but many of the earlier Carp occur in Lake Alexandrina in South reports throughout south-western Western Australia behind the artificial barrages Australia are likely to have been goldfish (Figure 2). When the barrages, built in 1930 (Brumley 1991; Breheny 1996). Previous to eliminate the brackish estuarine water, are reports of crucian carp are likely to have open, allowing freshwater to flow into the been goldfish (Breheny 1996). Coorong lakes system, carp also move out Breheny (1996) reported self-maintaining with the freshwater but die if they move into populations of Koi carp in the Blackwood more saline water (H. Jones, Southern River, but suggested that those in the Fishermen’s Association, Meningie, South Swan–Avon, Canning, Harvey, Murray and Australia, pers. comm. 1998). Wesley Rivers did not appear to be self-maintaining. The distribution of cyprinids now 2.2.5 Queensland covers most of the south-west corner of the State, from Geraldton to Albany (Twyford Rivers 1991; Breheny 1996). In Queensland there have been reports of Fisheries WA is compiling a database on carp carp upstream of weirs at Millmerran in the sightings. There are confirmed populations Condamine–Balonne catchment but the fish of carp in Yenchep National Park (Moore- are believed to be goldfish. Recent intensive River catchment) that have been established sampling in the upper Condamine near for at least 40 years and there are significant Warwick has not recorded a single carp (D. Koi carp populations in and around Moffat, Queensland Department of Natural Rockingham and Mandurah. Carp appear to Resources, pers. comm. 1998). The cyprinid have self-maintaining populations in most of reported in past surveys of Queensland the freshwater streams which flow into the coastal streams is more likely to have been Swan River and associated wetlands. There

Managing the Impacts of Carp 31 are also populations of carp, including Koi 2.2.8 T asmania carp, in water bodies in the south-west including the Blackwood River, Margaret Lakes River and nearby private dams. Carp were first found in Tasmania in 1974 Impoundments and artificial lakes (Figure 2) but were presumed to be eradicated after poisoning (Sections 1.3.5 and 6.3.5). Many artificial lakes built in subdivisions for However, carp were confirmed in Lake drainage purposes contain carp (for exam- Crescent in the Great Lakes district of the ple, Alexander Heights, Emu Lake and oth- highlands (Fulton and Sanger 1995; Diggle ers) which may have been introduced delib- and Jarvis 1998). Further surveys confirmed erately by developers and local residents. the presence of carp in the adjoining Lake Sorell (Brumley 1996). Although naturally Estaurine systems and coastal formed in the Great Plains, these lakes form lakes part of a hydroelectricity scheme and are connected to other water bodies. The lakes Koi carp are likely to have been stocked in are popular for trout fishing. Carp do not the lakes along the coastal strip from the appear to have spread to surrounding waters Swan River to the Murray River in Western but containment is likely to be difficult in the Australia. A report of release of Koi carp by future (Section 6.3.5). McKay (1977) was into an artificial pond created by road construction near the Swan River in 1971. This pond drained into the Swan River. Carp are now found in many freshwater bodies in south-west Western Australia.

2.2.7 Australian Capital T erritory Rivers In the Australian Capital Territory, carp are present in the Molonglo, Paddys, Cotter, Queanbeyan and Murrumbidgee Rivers. Carp are absent from the Cotter River upstream of Cotter Dam, which was constructed prior to the establishment of carp in the Australian Capital Territory (M. Lintermans, Environment ACT, pers. comm. 1998).

Impoundments and artificial lakes In the Australian Capital Territory, carp occur in all three urban lakes. The status of carp in these urban lakes has been regularly monitored since the mid 1970s. Carp regularly contribute more than 80% by number of the catch, although numbers appear to have declined slightly in the 1990s (M. Lintermans, Environment ACT, pers. comm. 1998).

32 Bureau of Rural Sciences 3. Biology and ecology

Summary Carp carry a number of disease organisms. Some of these now occur in Australia, such Carp are the largest member of the Family as the Asian fish tapeworm, and have poten- Cyprinidae in Australia and are often con- tial to pose risks to native fish species. Others, fused with goldfish. Interbreeding between such as the virus causing Spring Viraemia carp and goldfish produces hybrid individu- of Carp Disease, cause high mortality in als which resemble both species. Carp typi- Europe but do not currently occur in cally have flexible habitat requirements and Australia. live in low-altitude rivers or standing waters in mid-latitude regions. They have broad In Australia, carp migrate throughout the environmental tolerances and thrive in year, with some marked individuals record- habitats that have been disturbed by human ed as moving over 200 kilometres in a few activities, such as alteration of river flows, months. Large numbers of carp have been removal of instream habitat, reduced water recorded moving upstream during low flow quality, nutrient enrichment and removal periods accompanied by rising water tem- of streamside vegetation. peratures during spring and summer. Carp feed by filtering small particles from Carp are not normally predators of other the water or by sieving food items from sedi- fish, but small carp may be an important ments. They have no teeth in their jaws to part of the diet of larger predators. cut or hold food items, but have small, Competition for food and space between molar-like pharyngeal teeth in their throat to carp and native species is poorly under- chew and crush food. In Australia, carp lar- stood. By growing quickly to a large size vae feed on small zooplankton. As carp and feeding at low levels of the food chain, grow, they gradually take larger crustaceans carp may act as an energy trap, preventing and aquatic insects along with some plant transfer of energy to populations of other material. large fish. Female carp mature at between 2–4 years of Before carp began to spread in the late age and may produce more than one million 1960s and early 1970s, aquatic environ- eggs each year. Eggs are normally shed on ments in Australia were subject to numerous fibrous plant material in spring to early sum- disturbances that contributed to the decline mer. Females may spawn several times in one of native fish species. As populations of season. Juvenile carp frequent both shallow native fish have continued to decline, carp floodplain habitats and river channels, and have become well-established, mostly in dis- mortality may exceed 98% in the first year of turbed habitats, to the point where carp are life. Young carp are more abundant in habi- now the dominant species in many fish tats where the density of adult fish is relative- communities in south-eastern Australia. ly low. Growth rates of carp vary greatly between regions, depending on temperature, food supply and population density. 3.1 General description Survival of carp appears to be density- Carp (Cyprinus carpio) belong to the Order dependent. This means that when carp Cypriniformes, which are characterised by numbers are high, although large numbers having a protractile upper jaw, a mouth (jaws of eggs and juveniles are produced, only a and palate) without teeth, no scales on the small number survive. The implication of head, and usually lacking an adipose fin this for reducing carp populations is that (Helfman et al. 1997). The Family Cyprinidae, when the size of a population is reduced, to which carp belong, is further characterised survival rates of eggs and juveniles increase, by having from one to three rows of pharyn- and the populations rapidly recover. geal teeth, with never more than eight teeth in

Managing the Impacts of Carp 33 dorsal fin

lateral line

otolith

barbels caudal fin operculum pectoral fin

anal fin

phanyngeal teeth ventral fin

Figur e 3: Key features of carp anatomy (sketch by Craig Mills)

any row. In addition to these features, carp Table 4: Length:width ratio of the large pharyngeal have an elongated body with a slightly raised teeth in carp (Cyprinus carpio), goldfish (Carassius back. They possess a single dorsal fin with a auratus) and hybrids (Pullan and Smith 1987). stout, strongly serrated spine. Carp and their Reproduced with the permission of SIR Publishing. relatives lack the true spines of higher teleosts. Character Carp Hybrid Goldfish The spines of carp are actually hardened bony structures modified from the first ray of the 1st tooth 1.8 2.5 4.2 dorsal and anal fins. The dorsal fin originates 2nd tooth 1.5 2.8 5.0 anterior to the insertion of the abdominal pelvic fins, and consists of 3–4 spines and 3rd tooth 0.9 2.1 2.8 15–24 soft rays. The anal fin is small with three 4th tooth - 0.9 1.1 spines and five soft rays. The pectoral fin consists of one spine and 15–16 soft rays. The Some variation occurs in the degree of scale scales are large and cycloid with 33–40 scales development. In the Murray–Darling basin, along the lateral line. The tail is deeply forked. about five percent of individuals are not Carp also possess two pairs of fleshy whiskers, completely covered with scales. These fish or barbels, at either corner of the mouth, with have a smaller number of large, silvery scales the posterior pair being the largest (Figure 3). along the mid-line or scattered elsewhere on Carp posses three rows of pharyngeal teeth on the body, and are called ‘mirror carp’ the lower elements of the last gill arch on each (Cyprinus carpio) because of the reflective side. The two outer rows contain only a single properties of these scales. Another form tooth, while the inner row has three teeth known as ‘leather carp’ (C. carpio) lack (Figure 4), giving a pharyngeal tooth formula scales entirely, although this variant is partic- of 1,1,3:3,1,1. This characteristic formula is ularly rare in Australia. important for distinguishing between carp and other cyprinids (Table 4).

34 Bureau of Rural Sciences Carp can grow to large sizes, with reports of fish as long as 1200 millimetres and weighing 60 kilograms (Brumley 1996). Fish up to 10 kilograms are relatively common in south- eastern Australia, but fish from 50 grams to 5 kilograms are more common.

‘Carp are occasionally confused with goldfish which have reverted to their natural colouration of olive-bronze.’

In the wild, carp are occasionally confused with goldfish (Carassius auratus) which have reverted to their natural colouration of olive-bronze. Wild goldfish are often incorrectly called crucian carp (Carassius carassius). Goldfish are generally smaller, deep- bodied and plumpish in comparison to carp. Goldfish have 26–34 lateral line scales and a pharyngeal tooth formula of 0,4:4,0 (Table 4). The two species can be easily distinguished because goldfish lack barbels and their dorsal fin originates posterior to the insertion of the abdominal pelvic fin. The tail of goldfish is not as strongly forked as in carp. Carp and goldfish occasionally interbreed, producing hybrid individuals which possess varying combinations of features of both Figur e 4: Pharyngeal teeth of: (a) carp (Cyprinus car- species. Hybrids have reduced barbels or pio); (b) goldfish (Carassius auratus) and (c) hybrid may lack barbels completely and have 29–35 (Pullan and Smith 1987). Reproduced with the lateral line scales. The pharyngeal tooth for- permission of SIR Publishing. mula in hybrids can be either 1,4:4,1 or 2,4:4,2. Table 2 lists the diagnostic characters of carp and other cyprinids in Australia. ‘Carp can grow to large sizes, with reports of fish as large as 3.2 Habitats 60 kilograms.’ Knowledge of the habitats in which carp occur, and conversely, those in which they The colour of carp is variable, and may be do not occur, is important for developing bronze or olive-gold dorsally, softening to strategies for managing the impacts of carp. pale yellow or whitish on the flanks and ven- Strategies may include rehabilitation of trally. Some individuals may have a relatively degraded environments to make habitats less uniform, bright gold coloration. Koi carp are suitable for carp and more suitable for native a selectively bred ornamental carp variant, species. In habitats where carp do not yet originally from Japan. The domesticated occur, strategies to prevent carp invasion forms of Koi carp have a broader range of may be a high priority. colours and body-forms than the wild forms. The impacts and ecology of Koi in the wild are the same as other strains of carp.

Managing the Impacts of Carp 35 (a)

(b)

Evidence in Victoria that carp are not universally associated with degraded habitats: (a) Tambo River with carp, (Source: Keith Bell, K&C Fisheries), and (b) Wannon River without carp, (Source: Department of Natural Resources and Environment, Victoria).

36 Bureau of Rural Sciences 3.2.1 Typical carp habitats prevents any one species from dominating other species (Connell 1978). Increased dis- Carp are ecological generalists that live in a turbance as a result of human activity is wide range of habitats in Australia and over- therefore likely to cause local extinction of seas. They typically inhabit mid-latitude, more sensitive species. Reduced disturbance low-altitude, slow-flowing rivers as far provides an opportunity for species that pre- downstream as tidal freshwaters and even fer stable conditions to become dominant in enter estuaries. They also live in standing the new environmental regime. This con- waters ranging from small billabongs and cept, introduced by Connell (1978) as the ephemeral wetlands to large lakes and reser- intermediate disturbance hypothesis, pro- voirs. In New South Wales, carp are rare at vides some explanation as to why intro- altitudes above 500 metres (Driver et al. duced species tend to become established in 1997). They are less common in clear, cool disturbed environments. In this way, both swift-flowing streams. Carp are particularly increased or decreased disturbance may tolerant to poor water quality, and can sur- allow exotic species to become established vive in low oxygen concentrations, turbid (Ross 1991). Regulation and diversion of water and moderate salinities, and they have river flows reduces the natural disturbance higher tolerances to toxicants than many regime in riverine habitats and has allowed other species. Carp are well adapted to feed- carp to establish populations in modified ing from the bottom, taking mouthfuls of and relatively stable environments. sediment into their mouth and expelling inedible particles. This mode of feeding Types of habitat disturbances that are con- requires fine sediments and is not possible in ducive to carp and other opportunistic intro- habitats where the bottom consists of larger duced species have been recently sum- gravel or cobbles. Carp spawn in shallow marised by Driver et al. (1997) and Harris vegetated habitats, such as flooded grasses (1997). In coastal rivers of New South Wales, around the fringe of billabongs, lakes and carp were only found in lowland rivers floodplains (Section 3.4.2). where flows were regulated, and which are associated with large human populations. ‘Regulation and diversion of The broad environmental tolerances of carp suggest that the species may be less affected river flows has allowed carp to than other species by disturbances resulting establish in relatively stable from human activities. Disturbances may environments.’ occur both within the aquatic system, as well as within the catchment. Studies in Australia Koehn and Nicol (1998) found carp occupy a and overseas have found that carp become range of habitats, including woody debris more dominant in fish communities after dis- and habitats preferred by native species. In turbances to river flow, interference with rivers carp select slower water velocities stream connectivity, pollution and distur- close to the bank, and are also often found in bance to habitat structure (Whitley 1974; still billabongs and backwaters. Juvenile carp Sparks and Starret 1975; Hoyt and Robinson often occur in large numbers in inundated 1980; Winston et al. 1991; Gehrke et al. 1995; floodplain habitats and ephemeral creeks Driver et al. 1997; Harris 1997). following high flow events (Gehrke et al. In the Murray–Darling River system, flow 1999b). regulation to provide water for irrigation and hydro-electricity has reduced the variability Characteristics of disturbed of many inland rivers, allowing carp to take habitats that favour opportunistic advantage of a more stable environment exotic species (Gehrke 1997b). Gehrke et al. (1995) found that fish species diversity decreased directly Habitats that are moderately disturbed by with increasing disturbance of the natural natural events often have the highest species flow regime. A main factor in this reduced diversity because environmental variation diversity was an increasing dominance of

Managing the Impacts of Carp 37 carp. Gehrke et al. (1999b) also found that only persisted for two weeks (J. Diggle, carp recruitment was greatest in rivers with Tasmanian Inland Fisheries Commission, altered flow. pers. comm. 1999). Studies in Europe suggested an upper lethal temperature as high In coastal rivers, such as the as 40.6°C for carp (Horoszewicz 1973). The Hawkesbury–Nepean system near Sydney, actual temperature given as the lethal limit multiple disturbances such as flow regula- varies depending on the method used. Few tion for urban water supply, nutrient enrich- native Australian fish are able to tolerate ment and removal of vegetation, have creat- water above 35°C for any length of time. ed highly disturbed sites where introduced Carp have a greater tolerance of low dis- species such as carp and gambusia solved oxygen conditions than many (Gambusia holbrooki) are abundant Australian species, surviving levels of oxy- (Growns et al. 1998; Gehrke et al. 1999a). gen availability as low as 7% saturation at Hall (1981) noted that growth of the carp 5°C (Ott et al. 1980). At higher temperatures population in Lake Alexandrina in south- oxygen requirements increase, so that sur- eastern South Australia was typical of intro- vival near the upper thermal limit requires duced animals in a disturbed environment. close to 100% oxygen saturation. However, The lake was formed at the mouth of the the ability to survive in poorly oxygenated Murray in 1940 when barrages closed the water is not determined solely by oxygen mouth, changing the natural estuary into a tolerances. Carp and some native species are freshwater habitat. Extensive macrophyte able to respire from the thin surface film of growth in the shallow, non-flowing freshwa- water which contains more oxygen than ter environment probably did not suit the water below the surface (Kramer and native fish adapted to either the river or the McClure 1982; D. McNeil, La Trobe estuary, but allowed carp to flourish. University, unpublished data, 1999). Carp are often seen apparently gulping at the Catchment modifications such as clearing water surface. Many fish species have devel- vegetation, nutrient enrichment, disturbing oped adaptations such as modified gills, fine sediments and changes in stream mor- swimbladders, and intestines for breathing phology, all associated with agricultural and air, but such adaptations have not been urban development, have contributed to the demonstrated for carp. decline in native species distribution and abundance and an increase in carp abundance (Cadwallader 1978; Growns et al. ‘The ability of carp to survive 1998; Faragher and Harris 1994; Rinne 1990; periods of poor water quality Metzeling et al. 1995; Brierly et al. 1996). gives the species a competitive advantage over many native fish 3.2.2 Envir onmental tolerances species in Australia.’ The ability of carp to survive periods of poor water quality gives the species a competitive Salinity advantage over many native fish species in Australia. Broad environmental tolerances In southern France, carp survive in a salt also help explain the success of carp in lagoon delta ecosystem where salinity is Australia in regions where there is a high about 14% (parts per thousand) (Crivelli incidence of habitat disturbance (Harris 1981), but their growth rates are poor and 1997; Harris and Silveria 1999). they return to freshwater to spawn. A similar tolerance of carp to 14% salinity is noted Temperature from the Caspian and Aral Seas (Banarescu and Coad 1991). Juvenile carp up to 40 mil- Carp can adapt to water temperatures as low limetres long have been found at sea in the as 4°C and as high as 35°C. In Tasmania, carp discharge plume of the Fraser River in have been recorded at water temperatures as Canada, at a maximum salinity of 13.9% (the low as 2°C, although these temperatures salinity of seawater is 35%) (Barraclough and

38 Bureau of Rural Sciences Robinson 1971), suggesting that carp are 3.3.1 Food captur e methods and capable of moving between adjacent rivers food pr ocessing via the sea during floods. Sarig (1966) suggested that the mouth struc- In Australia, carp moved into the Gippsland ture of carp limits their ability to catch food Lakes system despite increasing salinity of straight from the water but many studies the water (Section 2.2.2). Carp can be found show that zooplankton (small crustaceans) in the Gippsland Lakes when salinity is in the are common in carp diets (Section 3.3.2). range of 10–18% but move upstream into Carp mostly feed by either selecting or filter- fresher water at higher salinities (A. Brumley, ing small food particles from the water or East Gippsland Institute of TAFE, unpub- ingesting sediments from the substratum and lished data, 1998). The death of carp in the filtering out food items. In both methods Gippsland lakes in 1998 in salinities of food is sucked into the mouth along with 16–18%, suggests that carp in Australia have water and sediments. At the entrance to the similar salt tolerances to carp elsewhere in pharynx or throat, gill rakers form a meshed the world, and are capable at least of spread- structure that can sieve out larger items from ing between nearby rivers during floods. the ingested water and sediments, which are Australian carp from the Murray River, South expelled through the opercular openings Australia, survived in salinities of 12.5% after behind the gills. This behaviour can notice- a direct transfer and 50% of carp survived at ably stir up fine sediments and increase tur- salinities of 15% after acclimation (Geddes bidity (Section 5.3.3). 1979). ‘Carp feeding behaviour and diet pH may provide opportunities to develop control methods that are The recorded lower pH limit for carp in Europe is below 5.0, which is higher than for selective for carp.’ other European and North American species (Hellawell 1986), but their upper pH lethal Items down to 0.5 millimetre can be retained limit is higher than most other species, at in the pharyngeal sieve formed by the gill rak- above 10.5. ers while smaller particles are expelled (Sibbing 1982). Because carp lack strong bit- Chemical pollutants ing teeth to cut large food items into smaller ingestible pieces, the upper size of their food Carp tend to be more tolerant than other fish is limited by the relatively small size of their species in the northern hemisphere to chem- pharynx. Large inedible items are expelled icals such as chlorine, selenium, the herbi- through the mouth. The pharyngeal teeth of cide 2,4-D, the organochlorine insecticide carp are flattened, molar-like structures that endrin, and synthetic pyrethroids (Hellawell can process food items with a range of chew- 1986). Interestingly, carp appear to be slight- ing and crushing motions, but they are not ly more sensitive to copper and toxaphene highly specialised to handle particular food than some other species (Hellawell 1986). types (Sibbing 1991). These teeth enable carp to eat small molluscs and insects and some plant material but give very limited ability to 3.3 Feeding behaviour and diet hold and swallow active, struggling prey such as small fish. In contrast, pharyngeal teeth of An understanding of some of the impacts of other fish can be highly evolved for either carp in Australia and their ecological interac- holding struggling fish, crushing molluscs, tions with other species is provided by the slicing flesh, chewing crustaceans, cutting types of food eaten by carp and the ways plant material or sorting small food particles they capture and process their food. Carp (Hyatt 1979). Carp do not have a true stomach feeding behaviour and diet may also provide to store swallowed food. Instead, they have a opportunities to develop control methods long intestine which enables them to digest that are highly selective for carp. food items that require long digestion times.

Managing the Impacts of Carp 39 3.3.2 Diet to feed on chironomids, and only ate plant material such as pieces of plant tissue, seeds Carp are omnivores, eating any small food and filamentous green algae in the absence items that are plentiful. Their diet therefore of chironomids. varies between locations and from season to season, depending on food availability ‘Carp in Australia eat much the (Lammens and Hoogenboezem 1991). In same range of food items as overseas studies, benthic insects are consistently important dietary items both in wild carp in other countries.’ and cultured carp (USA: Sigler 1958; USSR: Guziur and Weilgosz 1975; Israel: Kugler and In Lake Alexandrina in South Australia, Hall Chen 1968; Zur and Sarig 1980; Indonesia: (1981) found zooplankton formed a large Vaas and Vaas Van Oven 1959). Carp were proportion of the diet of small carp. The gap reported to have a preference for chirono- between gill rakers was proportional to the mid larvae (small worm-like larvae of length of carp, so that large carp had relative- midges) in lakes and ponds (Sigler 1958) and ly large gaps between gill rakers, preventing aquaria (Zur and Sarig 1980). Small carp are all but the largest zooplankton from being known to eat microcrustaceans (Matlak and filtered out. Plankton samples revealed many Matlak 1976; Zur and Sarig 1980). Adult carp taxa of microcrustaceans were present in the in marshlands in southern France fed on midwater. Cladocerans Daphnia spp. was a benthic insects and swimming insects (bee- common food item in most sizes of carp, and tles), microcrustaceans, detritus and seeds was apparently selected when in short sup- (Crivelli 1981). Seeds contain carbohydrates ply. In this study corixids were absent in the and carp feeding on seeds may be preferen- diet even when abundant in the water, tially seeking carbohydrate-rich high-energy whereas large amounts of detritus occurred food. in gut contents (Hall 1981). This suggests that the carp were feeding in midwater and In Australia, Vilizzi (1998) found the diet of from the bottom, but not swimming after young carp in backwaters of the lower fast-moving insects. Murray River contain small crustaceans (cladocerans, copepods, ostracods, These studies show that carp in Australia eat decapods), aquatic insect larvae (chirono- much the same range of food items as carp mids, corixids) and seeds. Older juveniles in other countries, and that the range of prey also had large quantities of sand in their guts, species available in Australia has not caused indicating that they had begun feeding from any substantial change of diet. the bottom. Hume et al. (1983a) found carp of all sizes in billabongs, lakes and rivers in Victoria fed on a variety of small inverte- 3.4 Population dynamics brates. Copepods and cladocerans were dominant in the diets of small carp, while Many methods proposed for the control of benthic insects, especially chironomids, carp populations and their impacts focus on dominated the diets of mid-sized carp reducing carp numbers. These methods (150–400 millimetres). Swimming insects share a common assumption that removing such as corixids (water boatman), some mol- carp will cause a sufficient reduction in carp luscs (snails) and terrestrial insects were also populations to reduce their impacts. eaten, reflecting the availability of all these However, if the number of carp removed is food types in carp habitats at the time of trivial compared to increases in carp popula- sampling. Microcrustaceans, for example, tions through recruitment and immigration, were common in the water and diet in spring then a great deal of effort can be expended and summer. Molluscs were only eaten for little or no reduction in impacts. when they were available in large numbers. Knowledge of the factors that influence the Aquarium experiments indicate that chirono- size and growth rates of carp populations is mids are a preferred food item. Hume et al. essential to guide decisions on managing (1983a) found that carp in aquaria preferred carp impacts and to assessing the effectiveness of control strategies.

40 Bureau of Rural Sciences 3.4.1 Population dynamics of fr esh- Carp spawning behaviour in other countries water fish in lakes and rivers is summarised in Breder and Rosen (1966), Scott and Crossman (1973), and Panek A number of fundamental differences exist (1987). After migration to suitable spawning between fish populations in lakes and rivers. habitats, spawning usually occurs in late Rivers are generally considered to be open spring or early summer, in water depths systems through which fish can migrate over ranging from so shallow that the fish can many hundreds of kilometres. For this rea- barely swim, to over one metre deep. son, fish populations at any location in a Preferred spawning habitats usually have river are usually open to both immigration abundant plant material. Several males may and emigration. The number of fish in the pursue a single female, nudging her to population, and their size and age distribu- apparently induce her to release eggs. tion at any one time, is likely to be deter- During the pursuit, spawning fish may thrash mined by recruitment rates (locally spawned around violently in the shallows, stirring up fish), mortality rates, immigration and emi- sediments as the backs and tails of the fish gration rates. break the water surface. Eggs are 0.5 mil- In contrast to rivers, many lakes contain pop- limetre in diameter and become adhesive on ulations that are effectively closed. This contact with water. They are shed over means that the lakes are connected to nearby aquatic vegetation, with eggs that do not rivers or other lakes so seldom that immigra- stick to vegetation falling into the sediments. tion and emigration are effectively zero. Males shed milt over the eggs as they are Population parameters in these populations released. Development occurs rapidly, with are more directly determined by recruitment eggs hatching in two days at 25°C and six and mortality rates and the influence of local days at 18°C. Although very large females environmental conditions. This makes the may contain up to seven million eggs, not all study and management of closed fish popu- the eggs are deposited at once, so that each lations in lakes simpler than for open popu- female may produce several batches of eggs lations in rivers. during one spawning season. ‘Preferred spawning habitats 3.4.2 Repr oduction usually have abundant plant Male carp in New South Wales were found to material.’ mature at 2–3 years of age, while females mature at 3–4 years of age (Brown 1996). In Victoria, carp were found to reach maturity In the Murrumbidgee Irrigation Area (MIA) earlier, at one year for males and two years near Griffith, New South Wales, Adamek for females (Brumley 1996). In both States, (1998) observed aggregations of mature carp age at maturity probably varies between at the entrance to lateral irrigation drains at habitats. The number of eggs produced by the end of September and in early October. female fish varies considerable according to Carp migrated into these drains during small the size, age and condition of individual fish. rises in water level. In contrast to reports Female carp produce from 80 000 eggs for from other countries, spawning carp formed fish of 1.25 kilograms, to 1 500 000 eggs for pairs swimming upstream. The male posi- fish of six kilograms (Hume et al. 1983a). tioned his caudal peduncle over the female’s Even though most fish with external fertilisa- and both eggs and sperm were released onto tion achieve close to 100% fertilisation of the the grass substratum. In pond experiments, eggs, mortality of eggs and larvae is com- carp spawned on a variety of substrates, monly high and may be density-dependent, including: the aquatic plant Myriopyllum making the number of eggs shed by a papillosum (common watermilfoil), live and spawning population an unreliable indicator dead grass and other terrestrial plants, river of the number of young fish surviving to red gum (Eucaplytus camaldulensis) branch- enter the population. es, and artificial plant substrata such as raffia mats, but did not spawn on muddy surfaces.

Managing the Impacts of Carp 41 Adamek (1998) found carp eggs from one and from the Paroo and Murrumbidgee spawning amongst flooded grasses in Barren Rivers and the Millewa Forest system in New Box Swamp, but not on any other natural South Wales between October and substratum. In Victoria, Hume et al. (1983a) December (P. Gehrke, NSW Fisheries, also found carp spawning on fibrous materi- unpublished data, 1992–95), indicating that al, with habitats containing grasses and spawning occurred before these times. Juncus spp. having the greatest number of Reports from the northern hemisphere sug- eggs. gest that the spawning season for carp may last as long as seven months (Crivelli 1981). Spawning in Australia has been reported to During prolonged spawning seasons with occur from September to December, warm temperatures above 20°C, carp in although the actual spawning period may be other countries may spawn several times, but shorter in specific locations. Spawning in the subsequent spawning may be prevented by MIA in 1997 was observed only from the onset of cooler temperatures. It has been October to early November, when water suggested that water temperatures above temperatures were 19°C–29°C. In the 25°C after fertilisation may reduce hatching Murrumbidgee River at Narrandera, carp success and increase the incidence of defor- spawned in late September 1993, with larvae mities in newly-hatched carp larvae (Penaz collected in early October and juveniles only et al. 1983) However, water temperatures in November (P. Gehrke, NSW Fisheries, above 25°C are common in much of the dis- unpublished data, 1993). In contrast, the tribution of carp and sensitivity of eggs to spawning period lasted from September to temperatures above 25°C has not been con- December in Victoria when water tempera- firmed for Australian populations. tures were 17°C–25°C (Hume et al. 1983a). Adamek (1998) suggested that warmer water temperatures may have caused the short ‘Fertility control techniques spawning season in 1997. require an understanding of the timing, length and pattern of ‘Spawning in Australia has been reproduction.’ reported to occur from September to December.’ An important aspect of carp spawning from the perspective of future control options Although minimum water temperatures are using fertility control techniques (Section often recorded as criteria for fish spawning, 7.3.8) is the timing, length and pattern of they are not an absolute requirement. For reproduction. Different approaches to fertili- example, carp were observed to have ty control might be needed for populations spawned in the Murray River by 10 October with individual females that do not shed all in 1996 when water temperatures were still their eggs at once but spawn several times in around 15°C (J. Koehn, Freshwater Ecology, one season, compared to populations with Department of Natural Resources and females that shed all their eggs at once but Environment, Victoria, unpublished data, have different females shedding their eggs at 1998). Carp larvae have normally been col- different times. This aspect of carp reproduc- lected in the Broken and Campaspe rivers in tion in Australia is not well understood. north-eastern Victoria from October until December (P. Humphries, Cooperative 3.4.3 Recruitment Research Centre for Freshwater Ecology, Recruitment occurs when the survivors from NSW, pers. comm. 1999) and in the Ovens the period of high juvenile mortality become River during September at water tempera- part of the adult population. Because juve- tures of 13°C – 14°C (A. King, Cooperative nile mortality is usually high, recruitment is a Research Centre for Freshwater Ecology, far more reliable indicator of potential popu- ACT, pers. comm. 1999). Larval and early lation growth than egg production. juvenile carp have been collected from the lower Murray River in October (Vilizzi 1998)

42 Bureau of Rural Sciences Nursery habitats occur in either temporary or suggest the existence of extensive recruitment permanent waters which offer food and shel- zones for carp in lowland regions, with sites ter for fish larvae and juveniles, and maximise on higher altitude slopes offering little suit- their chances of survival. Large numbers of able habitat for carp recruitment. juvenile carp were found in ephemeral flood- Thus while carp can spawn and successfully plain habitats in New South Wales (Gehrke et recruit in the absence of floods, they are al. 1999b), although the proportion of juve- opportunistic and move into shallow flood- niles in lake, river, creek and floodplain habi- plain habitats that contain relatively large tats varied greatly between river systems. In amounts of submerged vegetation for the semi-arid Paroo River system, juvenile spawning surfaces. These habitats also offer carp were most abundant in a shallow, inun- food and shelter for juveniles when suitable dated floodplain habitat. In the Darling River flows or floods occur. The increased avail- around Menindee, the floodplain was not ability of suitable habitats for spawning and inundated, but juvenile carp were extremely recruitment during floods means that recruit- abundant in an ephemeral creek. Riverine ment success is often much greater in years habitats consistently contained the fewest with large floods. Conversely, there is some juvenile carp. Juvenile carp were also uncom- evidence that carp do not spawn in dry mon in the main channel habitats of the years, which would prevent recruitment at Hawkesbury–Nepean River system in coastal these times (Hume et al. 1983a; J. Diggle, New South Wales (Gehrke and Harris 1996), Tasmanian Inland Fisheries Commission, supporting the notion that riverine habitats unpublished data, 1998). After floods, when constitute poor nursery areas. However, larval zooplankton proliferate, carp abundance is and juvenile carp have been collected in the likely to increase (Hume et al. 1983b; Gehrke main channels of the Campaspe and Broken et al. 1999b). rivers over several years, indicating that recruitment can occur in river channels with- Fish recruitment is often related to the size of out floodplain inundation (P. Humphries, the spawning stock, in the form of a stock- Cooperative Research Centre for Freshwater recruitment curve (Figure 5), which Ecology, NSW, pers. comm. 1999). describes the number of recruits in relation Length–frequency distributions of carp in to the number of spawning fish in the popu- New South Wales (Harris and Gehrke 1997) lation. Stock-recruitment relationships for Number of recruits

Number of spawners

Figur e 5: Theoretical stock-recruitment relationship for fish populations. At low population densities, small increases in the number of spawning females may result in large increases in recruitment. At high population densities, further increases in the number of spawners may lead to reduced recruitment. Conversely, at high population densities, a reduction in the number of spawning fish may actually allow increased recruitment to reduce or nullify the advantages of population reduction.

Managing the Impacts of Carp 43 other fish species sometimes show a rapid increase in the number of recruits as the 4000 number of mature fish in the population increases. As the spawning population grows, the number of young fish that survive 3000 may level off, or even decline after reaching a maximum. Density-dependent factors may strongly influence juvenile survival, so that higher fish population densities do not nec- 2000 essarily produce more recruits, and the number of young fish surviving may actually decline. The implication of this for reducing carp populations is that the size of the repro- 1000

ducing population will need to be substan- Number of recruits per hectare tially reduced to have any marked effect on recruitment to the population. In a population simulation analysis, Thresher (1997) 0 suggested that carp harvesting in the 0 100 200 300 400 Murray–Darling system would need to Number of spawners per hectare reduce the population of carp to an unknown point somewhere below 10% of the pre-fished biomass to create a relatively Figur e 6: Relationship between carp recruitment and stable, low population density for carp spawner abundance in New South Wales, based on data (Section 7.3.6). At such a low density, carp from Harris and Gehrke (1997). Each point represents populations would be in the relatively flat one river site. Populations with high carp densities have part of the logistic population growth curve, relatively low recruitment, but recruitment to populations with intermediate densities varies greatly, so that only a small number of carp would from very low to maximum values. need to be removed annually to prevent population growth. Stock-recruitment rela- because years of data were not available. For tionships may provide valuable information this analysis, all fish less than 155 millime- on the reproductive status of a population. tres, the average length of a one-year-old However, actual data points around the carp in the lower Murray (Vilizzi and Walker curve may vary greatly as a result of density- 1999), were considered to be recruits dependent factors and environmental varia- because the sampling methods used did not tions, so that the underlying stock-recruit- catch larvae and small juveniles. Similarly, all ment relationship may not be apparent in fish larger than the average length of a two- data collected from real populations. year-old fish were assumed to be sexually mature, and were considered part of the ‘Increased availability of spawning population. The figure shows suitable habitats for spawning large variations from the fitted line, indicat- and recruitment during floods ing both variable reproductive output and means that recruitment success variable survival to recruitment, depending is often much greater in years on environmental conditions. This relation- with large floods.’ ship is also affected by unknown rates of immigration and emigration from each site. It suggests that sites with relatively large num- Figure 6 shows a form of stock-recruitment bers of adult carp contain relatively few relationship for carp in New South Wales recruits, whilst maximum recruitment occurs rivers, using data from Harris and Gehrke in sites in the low to intermediate range of (1997). Stock-recruitment relationships are spawner abundance. However, sites with usually fitted to data obtained over many small to intermediate populations can also years, but in this case, the relationship was have very low recruitment, presumably fitted to carp populations at different sites depending on environmental conditions.

44 Bureau of Rural Sciences This example suggests that the density of mature carp needs to be reduced to below approximately 100 fish per hectare before further reduction can be expected to result in reduced recruitment under average conditions. Even then, however, high recruitment may still occur with numbers of mature carp as low as 35 fish per hectare. Therefore, reducing the size of the spawning carp population may not result in a noticeable reduction in carp recruitment unless the population can be reduced to a very small size. Similarly, reducing the number of carp that produce Figur e 7: Otolith from a carp showing six annual growth eggs, or reducing the number of eggs pro- bands (arrow heads). N nucleus, V ventral, D dorsal, A anterior, P posterior (photograph taken by L. Vilizzi). duced by fertile individuals by using some form of contraception (Section 7.3.8), might not result in reduced recruitment unless very high levels of infertility could be achieved.

‘The ability to modify aquatic ‘Growth rates of carp can be environments creates highly variable, depending on opportunities to significantly water temperature, food reduce carp recruitment, which availability and fish density.’ may provide more effective population control than Carp have been reported to live for more removing adult carp.’ than 15–17 years (Sarig 1966), growing to a size of 18–26 kilograms. Anecdotal evidence Because the impact of environmental condi- suggests that ages of up to 60 years or more tions on carp spawning and larval survival is may be attained in Europe. The largest carp so large, the ability to modify aquatic environ- measured from the lower Murray River by ments, for example, by altering flow, inunda- Vilizzi and Walker (1999) was a female that tion or temperature regimes, creates opportu- weighed 6.88 kilograms which was only nities to significantly reduce carp recruitment, seven years old. The oldest fish in their study which may provide more effective population of 603 carp was a 15 year-old female that control than removing adult carp. weighed 5.54 kilograms. Recently, a carp from the Murray River was estimated to be 23 Age and growth years old based on otolith bands (P. Brown, Marine and Freshwater Resources Institute, The age of many species of fish can be esti- Victoria, pers. comm. 1999). mated from banding patterns on scales, bones Like other fish species, growth rates of carp and otoliths (ear bones). Alternating periods can be highly variable, depending on water of slow and rapid growth associated with sea- temperature, food availability and fish densi- sonal conditions may produce bands on these ty. Carp in isolated water bodies, such as bil- hard structures that correspond to annual labongs, may stop growing altogether as growth patterns. Carp in Australia have food resources become depleted. Growth proven difficult to age accurately using scales may recommence rapidly when flooding (Hume et al. 1983a). Modern techniques stimulates food production (Hume et al. based on otoliths tend to be much more reli- 1983a). Figure 8 indicates sizes that can be able than earlier methods using scales. Vilizzi attained and the degree of variation in et al. (1998) and Vilizzi and Walker (1999) growth rates in different regions. Carp in have recently developed procedures to esti- Lake Crescent, Tasmania, appear to grow mate the age of carp from otoliths and opercu- more rapidly for the first two years than lar bones (Figure 7).

Managing the Impacts of Carp 45 700 6000 800

700 600 5000

600 500 4000 500 400 3000 400 Weight (g) Weight Length (mm) 300 300 2000 Length (mm) 200 200 1000 100 100

0 0 0 02 4 6 8 10 12 14 16 0 2 4 6 81610 12 14 Age (years) Age (years)

ddlhfklhffl lddl Murray length (mm) Figur e 9: Predicted lengths (fork lengths) for female Murray weight (g) (solid) and male (dashed) carp at different ages from the Tasmania length (mm) lower Murray River (Vilizzi and Walker 1999). Tasmania weight (g)

Figur e 8: Average length (fork length) and weight of 3.4.4 Mortality — pr edators, fish- carp at different ages in southern Australia. Values for ing, diseases and parasites the lower Murray River from Vilizzi and Walker 1999. Values for Tasmania from Vilizzi and Walker 1998. Survival of carp in the Murray–Darling sys- Regional differences in fish sizes at a given age can be tem appears to be strongly density-depen- dramatic. dent so that even though large numbers of juveniles are produced, limited resources such as food, and high predation mean that those in the lower Murray River, but by three only small numbers survive (Section 3.4.3). years of age, fish from the Murray are larger (Vilizzi and Walker 1998, 1999). The cold Gehrke et al. (1999b) found large numbers of temperatures in Lake Crescent would nor- juvenile carp in four rivers of the mally be expected to cause slower growth Murray–Darling River system in New South than in the Murray River. However, the low Wales but relatively few older individuals carp density and good food supply in Lake (Figure 10). Using estimates of length for carp Crescent may have allowed faster growth. of different ages in the lower Murray River More recent data from Lake Crescent suggest (Vilizzi and Walker 1999), mortality in succes- that carp of all ages are now growing at simi- sive year classes can be estimated. Estimates of lar or slightly slower rates to carp in the mortality require making a number of assump- Murray River (J. Diggle, Tasmanian Inland tions about: (1) the number of fish originally Fisheries Commission, unpublished data, produced in each age group (it is assumed that 1999). Carp of a given age in other locations recruitment is constant from year to year), (2) may differ markedly from these estimates. the ability to sample all ages representatively, For any given age, females tend to be slightly (3) emigration and immigration rates, and (4) larger on average than males (Figure 9), growth rates for fish from different areas. All although there is a large amount of variation four of these assumptions require validation both within and between sexes (Vilizzi and by further study. Because of these necessary Walker 1999). qualifications, estimates given here provide only a possible indication of the rate of carp mortality in the Murray–Darling Basin, and more accurate figures are required.

46 Bureau of Rural Sciences 600 Paroo

0+ 1+ 2+ 3+ 4+ 5+ 400

200

600 Darling

400

200

600

Number of fish Murrumbidgee

400

200

600 Murray

400

200

0 0 100 200 300 400 500 600

Fork length (mm)

Figur e 10: During a survey of habitats around the Paroo, Darling, Murrumbidgee and Murray Rivers from 1992 to 1995, juvenile carp up to one-year-old were abundant, but as a result of high mortality, older age classes were present in relatively low numbers (data from Gehrke et al. 1999b).

Of the four rivers considered, carp in the than these figures suggest because the data Paroo River had the lowest estimated mortality include very few larvae and juvenile carp too in the first year, at 83%, with values of 88% in small to be caught. However, these estimates the Darling, 96% in the Murray, and 98% in illustrate the point that very few carp actually the Murrumbidgee Rivers. True mortality in survive the first year. In the second year, mor- the first year is almost certainly much higher tality rates were generally lower, at 60%, 44%

Managing the Impacts of Carp 47 and 60% for the Darling, Murrumbidgee and Carp are known to be susceptible to a range of Murray Rivers, with only the Paroo River diseases (Section 5.3.7, Table 5). In Europe, recording high mortality at 88%. After the first the Spring Viraemia of Carp Virus (SVCV) year, the average mortality rate, across all four (Rhabdovirus carpio) has been identified as rivers, was 52%. Environmental variability, causing Spring Viraemia of Carp Disease, such as droughts, floods, temperature fluctua- which occurs on carp farms in spring and tions and extreme events such as algal blooms early summer (Crane and Eaton 1997). The can dramatically alter fish mortality. For this disease has not been recorded in wild carp reason, actual mortality may vary widely populations. Mortality from the disease ranges above and below estimated rates. from 5% to 100% of exposed fish, but is more commonly between 20% and 40% (Crane and Eaton 1997). SVCV has not been detected in ‘Mortality of carp as a result of Australia, but because carp have been brought predation by native fish and to Australia from Europe as well as from other birds may be a fruitful area for locations, it is possible that SVCV already research into carp control.’ exists in Australian waters (Crane and Eaton 1997). The virus is not specific to carp and can infect a wide range of species. The susceptibil- Juvenile carp are at the highest risk of preda- ity of Australian native species has not been tion by fish such as Murray cod tested extensively. In Europe, Spring Viraemia (Maccullochella peelii peelii), golden perch of Carp outbreaks are most severe in years (Macquaria ambigua) and redfin perch with long cool spring seasons where the water (Perca fluviatilis), and fish-eating birds such temperature stays between 10°C and 15°C and as cormorants (Pelecanidae) and pelicans this environmental stress reduces the immunity (Pelicanus conspicillatus), but they grow of fish. Therefore, environmental conditions in rapidly (Vilizzi and Walker 1999) to a size mainland Australia, particularly the absence of where they have few predators. The abun- severe winters and the long hot summers are dance of piscivorous fish is now generally unlikely to be conducive to outbreaks of the low (Harris and Gehrke 1997) so that the disease. The occurrence of clinical disease is a numbers of juvenile carp eaten by other fish result of interactions between the host, may also be low relative to the size of the pathogen and environmental factors. For this carp population. In contrast, large flocks of reason, occurrence of disease in natural sys- cormorants and pelicans are commonly seen tems can be very variable and the presence of feeding on carp in floodplain wetlands and a disease organism does not necessarily result below dams and weirs, where they may in a disease outbreak. potentially cause high mortality. Mortality of Recently, a condition called Spring Carp carp as a result of predation by native fish Mortality Syndrome has been reported from and birds may be a fruitful area for research England and Wales (P. Bolton, Environment into carp control (Section 3.5.2). Agency United Kingdom, pers. comm. 1999). In contrast to natural mortality, which is high- This condition causes high mortality of wild est in larval and juvenile fish, mortality from carp in spring and summer, but the cause has human fishing targets adult fish. Because com- not been identified and appears to be distinct from Spring Viraemia of Carp Disease. mercial fishing is restricted to certain waters and because markets for carp are underdevel- A number of parasites and disease organisms oped, fishing mortality is low compared to the identified in carp are listed in Table 5. Those total population of adult carp. In areas where currently known to occur also in native fish carp fishing is expanding, annual fishing mor- and which pose a risk to native species tality will increase, but there are no estimates include: the fungus Saprolegnia; the proto- available of the anticipated mortality as a pro- zoans Myxobolus, Trichodina, Ichthyobodo, portion of the total population. As most carp Cheilodonella, Ichthyophthirius and caught by anglers are not returned to the Apiosoma; the monogeneans Dactylogyrus water, mortality is undoubtably high, but the and Gyrodactylus; the cestode Bothriocephalus; contribution of angling mortality to total mor- and the copepod Lernaea. Other known tality is unknown. parasites of carp may already occur in Australia but have yet to be identified.

48 Bureau of Rural Sciences Managing theImpactsofCarp Table 5: Disease and parasite organisms isolated from carp worldwide, effects of clinical disease, and known susceptibility of Australian native fish.

Group Pathogen Disease Effects Recorded in Native species Reference (common carp in known to be name) Australia susceptible

Viruses Rhabdovirus Spring Viraemia of Heavy mortality of juvenile carp No None Crane and Eaton 1997 carpio Carp Disease

Bacteria Aeromonas Goldfish ulcer Visible red ulcers on body Yes Silver perch Langdon 1989; salmonicida disease Humphrey and Ashburner 1993; Daly et al. 1994 Edwardsiella Emphysematous Small lesions progressing to No None Austin and Austin 1987; tarda putrefaction abscesses and gas-filled Fujiki et al. 1994 swellings in muscles Fungi Branchiomyces Gill rot Fungal hyphae invade and No None Reichenbach-Klinke 1973 sanguini destroy gill epithelium, obstruct blood flow Saprolegnia Cottonwool fungus Secondary infection following Yes Bony herring, Reichenbach-Klinke 1973; other stress Murray cod Langdon 1989

Protozoa Cryptobia cyprini Weakness disease Pathogenic blood parasite No None Reichenbach-Klinke 1973

Sphaerospora Kidney disease Kidney damage No None Reichenbach-Klinke 1973 cyprini

Myxobolus Tissue parasite Cysts in carp skin No Similar species record- Johnson and Bancroft 1918; muelleri ed in golden perch Reichenbach-Klinke 1973

Myxosoma Closely related to Cysts in gills, cerebral blood No Similar species Johnson and Bancroft 1918; dujadini, organism causing vessels recorded in golden Reichenbach-Klinke 1973; Myxosoma whirling disease perch and Murray cod Ashburner 1978 49 encephalica Reference Reichenbach-Klinke 1973; Molnar and Rhode 1988; Langdon 1989 Reichenbach-Klinke 1973; Langdon 1989; Rowland and Ingram 1991 Reichenbach-Klinke 1973; Langdon 1989; Rowland and Ingram 1991 Reichenbach-Klinke 1973; Langdon 1989; Rowland and Ingram 1991 Reichenbach-Klinke 1973; Ashburner and Ehl 1973; Langdon 1989; Rowland and Ingram 1991 Native species known to be susceptible Similar species recorded in golden perch and silver perch spp recorded Trichodina from Murray cod, trout cod, golden perch, silver perch, Macquarie perch, river blackfish, bony herring and western carp gudgeon Murray cod, trout golden perch, silver perch, Macquarie river blackfish, bony herring Murray cod, golden perch, Macquarie silver perch, Australian smelt, river blackfish and bony herring perch, Macquarie perch, silver Australian smelt, river blackfish and bony herring Recorded in carp in Australia Yes No Yes Yes Murray cod, golden Not recorded but probably occurs Ectoparasitic damage to gill Intestinal parasite, emaciation Effects epithelium especially of young carp in pond hatcheries Ectoparasitic damage to gill epithelium epithelium Skin haemorrhage leading to fungal infection (common name) Whitespot Enteritis Trichodiniasis Cheilodonelliasis Ectoparasitic damage to gill sp., Pathogen Disease Eimeria cyprini, Eimeria subepithelialis Trichodinella Trichodina domerguei Ichthyobodo necator Cheilodonella cyprini, Cheilodonella hexastichus Ichthyophthirius multifilis Group Protozoa

50 Bureau of Rural Sciences Reichenbach-Klinke 1973; Richards et al. 1994 Hoole and Nissan 1994; Dove et al. 1997. Reichenbach-Klinke 1973; Ashburner 1978; Langdon 1989; Rowland and Ingram 1991 Reference Reichenbach-Klinke 1973; Rowland and Ingram 1991 Reichenbach-Klinke 1973; Rowland and Ingram 1991 Reichenbach-Klinke 1973 No Native species known to be susceptible Similar species found on western carp gudgeons Similar species recorded from golden perch and silver Western carp gudgeon, Western carp gudgeon, Midgley’s carp gudgeon, Lake’s Flathead gudgeon, Australian smelt Murray cod, trout golden perch, Macquarie perch, silver perch, river blackfish No Recorded in carp in Australia No Yes No Yes No No Reichenbach-Klinke 1973 No Reichenbach-Klinke 1973 Effects Loss of nourishment fins Infection on body surface Epithelial thickening of gills No Encysted larvae in skin and other organs common name External gill parasite Blood flukeGut flukes Obstruct blood vessels No Carnation-head tapeworm Asian fish tapeworm Anchor worm Ectoparasite on gills, skin and sp.

Pathogen Pathogen Apiosoma piscicola Dactylogyrus anchoratus, Dactylogyrus vastator, Gyrodactylus Sanguinicola inermis Allocreadium isosporum, Allocreadium carporum Neodiplostomum perlatum Caryophyllaeus laticeps Bothriocephalus acheilognathi Lernaea cyprinacea Group Monogenea Protozoa Crustaceans Digenea Cestodes

Managing the Impacts of Carp 51 3.4.5 Migration Torrumbarry fishway on the Murray River between February 1991 and July 1992, refut- radiotracking by Koehn and Nicol (1998) ing Reynolds’ opinion (1983) that carp were showed carp are a mobile species. Large non-migratory. Mallen-Cooper et al. (1995) movements occurred both upstream and found that carp migration correlated with ris- downstream, with individuals moving up to ing water temperature rather than increased 230 kilometres between Yarrawonga and flow. Carp continued to migrate when flows Barmah on the Murray River in only a few remained low and stable, similar to the flows months. These movements occur throughout created below irrigation storages. This sug- the year apparently independent of water gests that regulation of river flows may temperatures as low as 8°C. Carp moved in favour carp over native species, whose and out of billabongs, anabranches and movements appeared to be stimulated by slower flowing or still waters. Unlike native increases in water levels (Mallen-Cooper et species, they often became trapped in off- al. 1995). river habitats after water levels receded. Mallen-Cooper et al. (1995) recorded the ‘Carp migration correlated with highest numbers of carp moving during the lowest flows. High numbers of carp were rising water temperature rather recorded when rising temperatures reached than increased flow.’ 20°C. Carp continued to move when temperatures began to fall from the maximum of The scale of these movements mean that 25°C but there appeared to be a sudden carp are capable of spreading quickly decline in movement when temperatures throughout river systems. This suggestion is decreased below 24°C. Koehn and Nicol reinforced by the disappearance of 350 (1998) also found that carp movements tagged carp released into two small bill- occurred over a wide range of temperatures. abong anabranches connected to the Carp appeared to prefer to move during the Murray River. No recaptures were obtained morning, or to a lesser extent the afternoon, over the next two years despite extensive rather than at dawn, dusk or during the night fish surveys in the area (J. Koehn, (Mallen-Cooper et al. 1995). Freshwater Ecology, Department of Natural Juvenile carp move into shallow inundated Resources and Environment, unpublished floodplain habitats during high flow events data, 1998). Reynolds (1983) found that in the Paroo, Darling, Murrumbidgee and tagged carp in the lower Murray River Murray Rivers (Gehrke et al. 1999b). These showed no directed migratory behaviour, lateral migrations provide small fish with but moved either upstream or downstream direct access to rich supplies of planktonic for distances up to 80 kilometres, with most food in floodplain habitats, as well as provid- fish moving less than 10 kilometres from the ing a refuge from stronger flows and preda- point at which they were tagged. The fact tors in main-channel habitats. that the lower Murray is heavily locked which impedes carp movements, and that the environment is more akin to a pond 3.5 Ecological interactions with low flows, and perhaps lacks a movement trigger, may have influenced carp No species can move into a new habitat movements (J. Roberts, CSIRO Land and without having some impact on the system. Water, ACT, pers. comm. 1999). During These impacts may be relatively minor, or Reynolds’ study, native golden perch and they may lead to total removal of one or silver perch (Bidyanus bidyanus) travelled more original species and dramatically hundreds of kilometres with some golden change the ecosystem balance. Carp in perch recaptured in Queensland after the Australia now have roles as predators, prey, 1974 floods. competitors and habitat modifiers that affect other species and ecological processes. Mallen-Cooper et al. (1995) recorded 16 000 carp passing upstream through the

52 Bureau of Rural Sciences 3.5.1 Carp as pr edators retaining zooplankton as an important part of their diet (Hume et al. 1983a). Where carp In Australia, carp are often accused of dam- occur in large numbers, it is possible they aging populations of native fish species by may reduce the standing stock of zooplank- feeding on their eggs and larvae. However, ton to such a degree that the remaining zoo- the evidence available and the feeding mor- plankton can no longer suppress algal phology of carp (Sibbing 1988) suggest that growth by grazing, contributing to algal fish are a negligible component of carp diets blooms (Gehrke and Harris 1994). Prey types (Sections 3.3.1 and 3.3.2). Carp have relative- found in the diet of carp are discussed in ly small, underslung mouths adapted for detail in Section 3.3.2. sucking in small food items from the bottom. In contrast, most fish that prey on other fish 3.5.2 Carp as pr ey have large mouths, either without teeth to enable them to swallow large prey whole, or One of the few perceived benefits of carp in with teeth to grasp or bite chunks out of their present-day aquatic ecosystems in Australia prey. The size and shape of the pharyngeal is their role as prey for piscivorous fish, such teeth of carp make it difficult for them to as Murray cod, golden perch and redfin grasp and handle large, struggling prey such perch, and piscivorous birds such as pelicans as fish. However, large adult carp have been and cormorants. As populations of many recorded with small fish in their guts on rare small native species have declined (Harris occasions (Hume et al. 1983a). Large carp and Gehrke 1997), their reduced availability have also been recorded herding schools of as prey may have had an impact on predator Australian smelt (Retropinna semoni) in the populations. The increased abundance of Murray River near Yarrawonga and appar- carp juveniles may have compensated to ently feeding on the smaller fish. Subsequent some degree for the loss of native prey inspection found Australian smelt in the gut- species. There is, however, no evidence that contents of each of 12 carp examined (Garry predator populations have improved as a Thorncraft, NSW Fisheries, unpublished result of the food supply presented by large data, 1998). numbers of small carp. It is more likely that the progressive decline in numbers of native ‘Carp may consume large piscivores has reduced predation pressure numbers of fish eggs.’ on carp, and assisted the expansion of carp populations. Large carp, too big to be consumed by fish and bird predators, are com- Scientists in several countries have hypothe- monly the only dead fish found around the sised that carp populations have a negative edge of receding waters (Brown 1996). feedback loop to suppress recruitment by preying on their own eggs or larvae. When ‘The decline of native piscivores adults are removed, predation on eggs and larvae is reduced, resulting in strong recruit- may have assisted the ment which rapidly replaces the removed expansion of carp.’ fish. There are, however, other density- dependent processes capable of producing In water storages where carp occur in large reduced recruitment at sites with high densi- numbers, potential exists for predatory ties of adult carp without invoking adult pre- native fish to be stocked to limit carp recruit- dation on eggs and larvae (Section 3.4.3). ment by increasing predation. Australian Carp are efficient grazers of zooplankton and bass (Macquaria novemaculeata) finger- biofilms attached to hard surfaces and may lings were released into Fitzroy Falls potentially consume large numbers of Reservoir, near the town of Robertson in attached fish eggs. As juveniles, carp feed New South Wales, in an attempt to control largely on zooplankton. As they grow carp and to improve angling opportunities. It beyond 150 millimetres, they progress to is likely to take 1–2 years before the young other forms of macroinvertebrates, while still bass are large enough to eat juvenile carp. This reservoir also contains rainbow trout

Managing the Impacts of Carp 53 (Oncorhynchus mykiss), which may also eat more species utilise a food source that is in small carp, but bass were stocked at the short supply. Earlier analyses suggested that request of local anglers who thought that competition between carp and some native trout (Salmonidae) were not thriving in this fish for food was unlikely, because native habitat. Fish make up only a small propor- fish tend to spawn during floods when zoo- tion of the diet of bass (Harris 1985), and if plankton are abundant in floodplain habitats trout appear ineffective at controlling carp (Reynolds 1987). However, recent evidence numbers, then it is questionable whether discounts this suggestion, as carp appear to stocked bass will provide any control of carp be equally as capable as native fish of by predation. Stocking golden perch and exploiting zooplankton blooms in shallow Murray cod to control carp in Lake Burley ephemeral habitats (Gehrke et al. 1999b). Griffin and Lake Ginnindera in the Australian The Victorian Carp Program reported an Capital Territory has had no obvious effect overlap in the diet of carp with small native on thriving carp populations (Lintermans fish such as Australian smelt and western and Rutzou 1990, 1992). carp gudgeon (Hypseleotris klunzingeri). It has been suggested that carp may have an While there is scope for stocking predators advantage over other species by spawning to control carp in impoundments, food chain earlier, thereby giving larvae and juveniles manipulations have a chequered and contro- access to food earlier than native species versial history (Sections 3.5.4 and 7.3.6) and which spawn later (Roberts and Ebner 1997). may not achieve carp control. Ecological While this suggestion appears logical, com- outcomes of stocking manipulations are dif- petition for limited food resources has not ficult to predict and may range from quali- been demonstrated (Hume et al. 1983a; fied success requiring ongoing management Gehrke et al. 1999b). to failure. Stocking fish is strictly regulated in most Australian States and Territories to avoid other potential problems with fish ‘Carp may have an advantage populations and to avoid creating additional over other species by pest populations. spawning earlier, giving larvae and juveniles access to food 3.5.3 Carp as competitors earlier than native species which spawn later.’ Carp may compete with native fish for food (exploitation competition) and habitat space such as spawning sites (interference competi- Competition between newly introduced tion). Since carp begin spawning at lower species and native species is believed to be water temperatures than most native fish, they extremely common but is notoriously diffi- spawn before many species and may exclude cult to demonstrate (Li and Moyle 1993). smaller species such as gudgeons (Eleotridae) Competition occurs when the niches of two and rainbowfish (Melanotaeniidae) from their or more species overlap. The niche of a preferred spawning areas in vegetated habi- species consists of the species’ total require- tats. Suggestions that carp may interfere with ments to survive under a range of environ- the nesting sites of freshwater catfish mental conditions throughout its distribution (Tandanus tandanus) are highly logical. and includes habitat preferences, environ- Such proposed interactions between carp and mental tolerances, diet, feeding behaviour native species have yet to be confirmed and spawning locations. Under any given (Section 5.3.4). environmental conditions, a species may use only a small part of its total requirements, for A degree of dietary overlap occurs between example, by feeding on only one type of carp and native fish feeding on zooplankton prey even though other prey are available. and other invertebrates, but whether these For this reason, measuring the niche of a food sources are available in such limiting species can be difficult. Without fully defin- amounts to cause competition is uncertain. ing the niche of two species, it is not possi- Competition for food can occur if two or ble to identify all the ways in which they may

54 Bureau of Rural Sciences compete. Demonstrating unequivocally that aquatic plants (Section 5.3.5), and (5) sup- competition actually occurs in wild popula- pression of aquatic plants by turbidity which tions is usually difficult. Consequently, while reduces light penetration (Gehrke and Harris it is intuitive that carp compete with native 1994, Section 5.3.3). There is growing inter- fish species in many ways, as illustrated est both in Australia and overseas in manipu- above, there are currently no clear examples. lating the composition of fish communities to reduce predation pressure on zooplank- 3.5.4 The r ole of carp in aquatic ton. In theory, this should allow zooplank- food webs ton populations to expand, and in turn, graze algae to low densities where they are Carp can attain immense biomass densities unlikely to develop problematic blooms. as a result of their large body size and great However, the validity of the concept is highly abundance. Reid and Harris (1997) estimated controversial at both international carp population density in the Bogan River (Carpenter and Kitchell 1992 versus De Melo at 11 316 fish per hectare, while biomass et al. 1992) and national (Boon et al. 1994 density estimates as high as 3 144 kilograms versus Matveev et al. 1994) levels. While not of carp per hectare have been made for the directed specifically at carp, these examples Lachlan River (Driver et al. 1997). It has been illustrate the effects that fish with diets simi- suggested that carp may act as an energy lar to carp can have on the ecology of food trap, limiting the transfer of energy to succes- webs in lakes. Similar interactions occur in sively higher levels in the food chain rivers. Riverine food webs, however, are (Roberts et al. 1995, Gehrke 1997a). Carp more difficult to manipulate experimentally obtain their energy from lower levels in the than food webs in lakes because of the com- food chain than large-bodied, piscivorous plex nature of river flows and the ability of native species such as Murray cod and gold- organisms to migrate upstream and down- en perch. However, because carp grow stream. rapidly (Brumley 1996; Vilizzi and Walker 1999) to large sizes that reduce the risk of 3.5.5 Carp r eplacing native predation, and are relatively long-lived, the fr eshwater fish energy in their bodies is not as readily available to higher predators as an equivalent Gondwanaland separated from the other biomass of small native species. High popu- continents about 100 million years ago and lation densities of large carp therefore repre- Australia separated from Gondwanaland sent a large pool of energy that is only trans- about 45 million years ago. Hence, the fresh- ferred to other parts of the food chain when water fish fauna of Australia evolved in rela- carp die. The dominance of carp in lowland tive isolation from other continents and rivers may therefore contribute to the Australia escaped the rapid, large-scale evo- observed decline in species richness with lution of primary freshwater fish (that is, increasing distance downstream (Gehrke species groups that evolved in freshwater), 1997a). such as carps and freshwater catfish, that occurred in the tropics and throughout ‘Carp may act as an energy trap south-east Asia. Instead, freshwater fish com- and alter nutrient transfer munities in Australia were dominated by through aquatic ecosystems.’ other families of recent marine origin such as basses and cods (Percichthyidae), grunters (Haemulonidae), freshwater catfishes, rain- Carp may also alter nutrient transfer through bowfishes, hardyheads (Atherinidae) and aquatic ecosystems through five possible gudgeons. pathways that contribute to algal blooms: (1) direct predation of algal grazers (Section Australian rivers are amongst the most vari- 3.3.2), (2) resuspending nutrients by disturb- able in the world (Puckridge et al. 1998) and ing sediments (Section 5.3.3), (3) excreting fish species have had to adapt to erratic and nutrients into the water, (4) direct damage to unpredictable riverine environments in order to survive. Although the total number of

Managing the Impacts of Carp 55 freshwater fish species native to Australia is impacts of trout and the lack of evidence for small, at between 180 and 200 species the impacts of carp (Wager and Jackson 1993, (Merrick and Schmida 1984; Allen 1989; Koehn 1995). Carp do, however, co-occur Paxton et al. 1989; McDowall 1996), this with six endangered species: Murray hardy- number of species in relation to catchment head (Craterocephalus fluviatilis), golden area is typical for regions with similar cli- galaxias (Galaxias auratus), trout cod, south- mates world-wide (Gehrke and Harris 2000). ern purple-spotted gudgeon (Mogurnda adspersa), Macquarie perch, and Oxleyan The decline and conservation status pygmy perch (Nannoperca oxleyana), as well of native fish species as a further seven species considered to be vulnerable: silver perch, Darling River hardy- Concern about declining numbers of native head (Craterocephalus amniculus), Yarra fish was raised as early as 1936 when fish- pygmy perch (Nannoperca obscura), Dwarf eries agencies from New South Wales, galaxias (Galaxiella pusilla), Murray galaxias Victoria and South Australia met to develop (Galaxias rostratus), non-parasitic lamprey plans to protect fish in the Murray River (Mordacia praecox), and the Australian (Anon 1936). By the time carp began their grayling (Prototroctes maraena). The interac- rapid expansion in the late 1960s and 1970s, tions or impacts of carp on these species are declining populations had become critical unquantified as causal links have not been for many native species, and commercial established. catches of Murray cod, golden perch and silver perch had already declined (Figure 11 ‘Carp could establish in Reid et al. 1997). In addition, migratory tropical Australia.’ species such as golden perch had become locally extinct upstream of major impoundments (Weatherley and Lake 1967), It has been suggested that as a result of the Macquarie perch (Macquaria australasica) decline of native species, aquatic habitats in had dramatically declined in distribution some areas are under-used by fish, and that (Cadwallader and Rogan 1977; Cadwallader carp have been successful in these areas 1981), distribution of Murray cod had because they have not had to compete become restricted, and trout cod against other species (Harris 1997). Similarly, (Maccullochella macquariensis) were disturbance may alter aquatic habitats, mak- reduced to only two small remaining popu- ing resources such as habitat space or food lations (Cadwallader and Gooley 1984). more suited to invasive species such as carp as opposed to native species (Section 2.1.4). Within the Murray–Darling Basin, widespread catchment changes over the past 100 Fish have been introduced successfully to years, and changes to river habitats such as many habitats around the world that have not nutrient enrichment, removal of bankside been greatly disturbed by humans and which vegetation, pollution, siltation, construction have diverse faunas. Where natural variation of dams and weirs, and flow alteration have prevents any species from becoming domi- contributed to the decline in native fish nant, and disturbance is at an intermediate species (Frith and Sawer 1974; Cadwallader level, mixed assemblages of native and intro- 1978; Harris 1984; Harris and Mallen-Cooper duced species are more likely to co-exist (Li 1994; Harris and Gehrke 1997; Section 2.1). and Moyle 1993). In Australian rivers, flow alteration and catchment disturbance have More than one-third of Australia's freshwater reduced the natural level of variability, con- fish species are considered to be under threat tributing to the decline in native species, and (Koehn 1995). Of these, 20 species are consid- creating conditions that favour establishment ered to be affected by interactions with intro- of introduced species (Gehrke et al. 1995; duced species. The majority of these threaten- Puckridge et al. 1998). The lack of native ing interactions are however, with species species with a similar niche to carp, which other than carp, including gambusia and trout. might otherwise provide strong competition, Reasons for this include the widespread has also favoured carp becoming established nature of gambusia, the more direct, predatory (Section 3.5.3).

56 Bureau of Rural Sciences 160 Murray cod period of major carp expansion in the 140 Murray–Darling Basin 120

100

80 60 Catch (tonnes) 40 20 0

50 Silver perch

20 Catch (tonnes)

0 350 Golden perch 300

250

200

150 Catch (tonnes) 100

0 45 Freshwater catfish 40 35 30 25

Catch (tonnes) 20 15 10 5 0 1977– 78 1947 – 48 1950 – 51 1953 – 54 1956 – 57 1959 – 60 1962 – 63 1965 – 66 1968 – 69 1971 – 72 1974 – 75 1980 – 81 1983 – 84 1986 – 87 1989 – 90 1992 – 93 1995 – 96

Year

Figure 11: Commercial catches of Murray cod, silver perch and golden perch in New South Wales declined in the early 1960s before the expansion of carp, disproving claims that the decline of native fish was caused by the major expansion of carp throughout the Murray–Darling basin coinciding with widespread flooding in the early 1970s. Good catches of golden perch and freshwater catfish were taken following record floods in 1974-75, but later declined (after Reid et al. 1997). Note varying scale on y-axes.

Managing the Impacts of Carp 57 Carp extend through most lowland and the bottom are also common. Ecological the- slopes rivers of inland south-eastern Australia, ory might, therefore, suggest that the combi- overlapping with native species such as nation of predation pressure, competition, Murray cod, trout cod, golden perch, high species diversity, low levels of human Macquarie perch, freshwater catfish, bony disturbance, environmental variability and herring (Nematalosa erebi), silver perch, water temperatures (Section 3.2.2) may help spangled perch (Leiopotherapon unicolor), to prevent carp from becoming established river blackfish (Gadopsis marmoratus) and in tropical Australian rivers. smaller species such as various gudgeons, However, there is no room for complacency hardyheads, galaxiids (Galaxiidae), Australian based on these facts. In Papua New Guinea, smelt and rainbowfish. carp are spreading in the lowland reaches In coastal rivers in south-eastern Australia, and floodplain habitats of the Sepik River the distribution of carp now overlaps the system following their escape from aquacul- range of native species such as Australian ture ponds in the highlands (Ulaiwi 1990). bass, estuary perch (Macquaria colonorum), This is despite the Sepik River containing a both long-finned (Anguilla reinhardtii) and broad range of tropical predatory species. short-finned (A. australis) eels, small galaxiid This tropical example, combined with the species, Australian smelt, Australian grayling, abundant aquatic vegetation in many tropi- various gudgeons, mullet (Mugilidae) and cal Australian rivers suggests that carp could river blackfish. Many forms of habitat alter- establish in tropical Australia. ation, including modified river flows and proximity to large human population centres, ‘There is no documented are features of coastal rivers where carp have evidence of native fish species become established (Driver et al. 1997; Harris being displaced or totally and Gehrke 1997; Marsden et al. 1997; replaced by carp in Australia.’ Gehrke et al. 1999a; Section 2.1.4). Carp have not become established in the In summary, carp co-occur with native fish rivers of tropical Australia, where the diversi- species and may compete in many ways, but ty of freshwater fish species is greatest there is no documented evidence of native (Beumer 1980; Bishop and Forbes 1991; species being displaced or totally replaced Pusey and Kennard 1996). Rivers in this by carp in Australia. Declines in native fish region retain much of their natural variabili- species, in conjunction with extensive habi- ty, are currently not regulated to the same tat disturbance, are likely to have facilitated degree as rivers in the south-east, and the expansion of carp populations. As an human population centres are smaller, creat- opportunistic species, carp have exploited ing less catchment disturbance. The tropical this situation to become well-established in riverine environments support a prolifera- Australia. tion of predatory fish species such as barramundi (Lates calcarifer), mangrove jacks (Lutjanus argentimaculatus), saratoga 3.6 Curr ent r esear ch (Scleropages leichardti), ox-eye herring (Megalops cyprinoides), jungle perch For a number of reasons that are not particu- (Kuhlia rupestri) and various grunters, along larly clear, there was little interest in carp with a diverse array of smaller perchlets research in Australia until the early 1990s (Kuhliidae), rainbowfish, hardyheads and (Roberts and Tilzey 1997). Fortunately, this gudgeons (Pusey and Kennard 1996; Bishop situation is changing to meet the knowledge and Forbes 1991). Other predators include requirements for proper identification, man- both freshwater (Crocodylus johnstoni) and agement and monitoring of problems associ- estuarine (C. porosus) crocodiles and a wide ated with carp (Table 6). variety of fish-eating birds. Several species of fork-tailed catfish (Arius graeffei), mullet and bony herring which feed largely from

58 Bureau of Rural Sciences NSW Fisheries, CRC for Freshwater Ecology, Queensland NSW Fisheries, CRC for Freshwater Ecology, Department of Natural Resources, Griffith University, Inland Fisheries Commission Tasmanian CRC for Freshwater Ecology NSW Fisheries, CRC for Freshwater Ecology NSW Fisheries, CRC for Freshwater Ecology Inland Fisheries Commission Tasmanian Inland Fisheries Tasmanian CRC for Freshwater Ecology, Commission University of Adelaide CRC for Freshwater Ecology, University La Trobe CRC for Freshwater Ecology, NSW Fisheries, CRC for Freshwater Ecology CRC for Freshwater Ecology Sydney University of Western CRC for Freshwater Ecology, Department Victorian of Natural Resources and Environment Department Victorian of Natural Resources and Environment University of Adelaide CRC for Freshwater Ecology, Organisation esearch in Australia Carp control strategies Hydrologic manipulation as a carp control strategy Effects of river management options, such as temperature regimes and environmental flows, in controlling carp and rehabilitating native fish populations Trends in commercial carp fisheryTrends NSW Fisheries, CRC for Freshwater Ecology Methods for reducing carp abundance and measuring environmental benefits Age and growth of carp Physiological tolerances of fish in billabongs Downstream transport of larval and juvenile fish Early life history and environmental tolerances of carp Surveys of carp populations, changes in densities, and recruitment patterns Effects of carp on plants and sediments Diets and competitive interactions between carp other species Carp recruitment sources and movements Effects of drying on lake ecology Growth, reproduction, mortality and population structures of carp Examples of current carp r Table 6: Table CategoryMonitoring Research area Impact (assessment) Control methods Ecological processes

Managing the Impacts of Carp 59 A Strategic Research Plan for carp is being Areas for research (Sections 10.2–10.6) developed as part the National Management include: Strategy prepared by the Carp Control • basic biology and ecology Coordinating Group. The plan will set priorities and focus carp research on the information needs of the National Management • population dynamics Strategy, and on knowledge gaps identified in this book. • population genetics The Fisheries Research and Development • habitat requirements Corporation has established guidelines for carp research as part of their funding pro- • distribution and abundance grams, but these guidelines have not been linked to other agencies, such as the Land • interactions with native species and Water Resources Research and Development Corporation. The Natural • impacts Heritage Trust provides some funding for carp research through the Murray–Darling • control techniques 2001 FishRehab Program as well as through RiverCare and the Fisheries Action Program. • recovery of aquatic ecosystems follow- Carp research is now being conducted by ing carp control. the Cooperative Research Centre for Freshwater Ecology, State natural resource The range of issues currently being investigat- and water management agencies in ed is indicated by the examples in Table 6. Queensland, New South Wales, Victoria, Tasmania and South Australia, CSIRO and a number of university research teams. A number of community groups are also conducting management-oriented research.

60 Bureau of Rural Sciences 4. Community attitudes and expectations

Summary 4.1 Attitudes fr om the norther n In contrast to the positive attitudes held hemispher e towards carp in Europe and Asia, carp are Initial Australian attitudes to carp (Cyprinus perceived as a pest in Australia. This attitude carpio) were influenced by those attitudes ranges from agriculturists and water authori- prevalent in the Northern Hemisphere. This ties, who believe carp cause extensive damage, began with a positive view of carp as a to attitudes of most recreational fishers and species to import during the time of the conservationists who consider carp a nui- Acclimatisation Societies of the 1860s to sance. Many groups, including conservation- 1880s. Carp were still favourably viewed at ists, scientists and those concerned for native the turn of the century (Stead 1929) when fish, such as recreational and commercial native fish were actually removed from fishers, believe that carp are often a scapegoat Prospect Reservoir, a large water storage for other environmental problems. Many peo- dam near Sydney, and carp and goldfish ple believe that carp cause declines in aquatic (Carassius auratus) stocked. Europeans plants and native fish and increase water tur- regard carp highly both as a target species bidity. Some people also believe that carp for anglers and as a table fish (Section 1.2). increase bank erosion and water nutrient An aquaculturist of European descent initiat- concentrations. Scientific evidence supporting ed the spread of the Boolara strain of carp in or refuting these negative perceptions is not Australia in the belief that he would be able always available. to breed up carp and sell them to farmers. There are many people who are unaware His business intention was to make money that carp are an introduced species which from farmers wishing to clear their dams and causes environmental problems. Carp have watertanks of algae and plants. now been established for long enough to In North America in the 1960s, the public allow a generation to have seen the species attitude to carp was negative following as a normal occurrence. Recreational reports of detrimental impacts on vegetation, ‘coarse’ fishers consider carp desirable and native fish and water quality (Tryon 1954; may be translocating them to new waters. Hendricks 1956; Mraz and Cooper 1957). Most people who consider carp to be a problem Such detrimental impacts were also attribut- would like to see them controlled. Commercial ed to carp in Australia even before investiga- harvesting of carp is considered a valid con- tion on their effects began (Butcher 1962 & trol option by many who believe harvesting 1967; Wharton 1979). This was a change in will at least reduce carp densities and at best attitude to carp by Australians, as the lack of ensure establishment of a market that could survival of carp in 1860 had been viewed as maintain carp numbers below the level where a failure. The successful colonisation of carp they are a problem. This viewpoint does not in the 1960s, as an introduced fish species always adequately consider whether high lev- with possible detrimental effects, was seen els of commercial harvesting could achieve as a disaster. this goal. There are also serious concerns that Although North Americans and Australians establishing a commercial carp harvesting are now concerned about the impacts of industry may hinder effective control mecha- carp (Chapter 5), the attitude towards carp in nisms, possibly leading to claims for compen- Europe and Britain has remained favourable. sation if an effective control method is devel- Carp have not increased to undesirable num- oped. Many conservationists, recreational bers in European waters. Several cyprinid fishers and indigenous people consider that species naturally coexist with carp and all the choice of control options for carp needs to have predators such as pike (Esox lucius) include rehabilitation of the catchments and (Smith et al. 1997). In Europe and Britain riparian areas concerned.

Managing the Impacts of Carp 61 carp are perceived to be in acceptable num- in Victoria complain that carp undermine bers and considered highly desirable by riverbanks causing erosion and trees to fall coarse anglers. A minority of anglers in in, although this seems quite improbable and Australia share this attitude, and concerns is likely to be a misconception (W. have been expressed at the establishment of O’Connor, Department of Natural Resource new carp populations for angling (Section and Environment, Victoria, pers. comm. 4.9.2). 1998). Problems with blooms of bluegreen algae (Cyanobacteria) in the Gippsland lakes, in Victoria, linked with nutrient 4.2 Public attitudes in Australia increases, are attributed by many of the public to increases in the number of carp in the The media has promoted the perception of lakes (M. Rankin, Gippsland Coastal Board, carp as an undesirable introduced species. A Victoria, pers. comm. 1998). In both these common view held in the general communi- instances, maybe carp are being used as a ty is that carp contribute to the degradation scapegoat for river health problems, espe- of river environments and that the problem cially uncontrolled stock access to water of reducing carp numbers needs public sup- bodies (W. O’Connor, Department of Natural port (Easton and Elder 1997). Generally Resource and Environment, Victoria, pers. there may be a lack of public knowledge comm. 1999). about carp and that it is an introduced fish. Carp have been established for long enough Some of the opinions from the New South that a generation has now seen the fish as a Wales survey, which were not widely held ‘normal’ component of fish communities in (rank 16), such as increased soil salinity their local waters. because of carp, and difficulties in watering livestock because carp scare animals away Sectors of rural communities in New South from watering points, are not strongly sup- Wales, including irrigation and dryland agri- ported by public opinion and have no scien- culture groups and angling associations were tific basis (Table 9; Section 5.3). surveyed on their opinions about carp and related issues (P. Gehrke, NSW Fisheries, The policy of the Murray–Darling Association, unpublished data 1998). The questions a local government group, which represents specifically avoided mentioning particular many water users in the Murray–Darling problems so that the responses reflected Basin, is: ‘Carp is a major cause of the decline either personal opinion or hearsay. Issues in the Murray–Darling Basin river system and raised in responses are grouped into cate- unless solved will render efforts to improve gories listed in Table 7. Because of the small river health ineffective. A major integrated number of respondents (27), these results effort to eliminate carp should be com- should be taken as an indication of what menced’ (L. Broster, Murray–Darling people think about carp, rather than a com- Association, South Australia, pers. comm. plete list of opinions. 1997). These issues, especially those ranked 1 to 7, ‘Evidence indicates that carp may reflect opinions commonly held about carp in other States of Australia. Some of these contribute to these problems problems may be caused by other factors. under some environmental For example, one response to the survey in conditions, but carp alone do not New South Wales commented that carp are cause the problems.’ the single most stressful factor affecting river health, however the same response ignored Jerry Killen, a spokesperson for the Irrigators the effects of large-scale water extraction and Association of NSW and a Water Users heavy use of agricultural chemicals in the Advisory Board member, considers that carp river system in which the respondents lived. have negative impacts and that their under- The less widely held opinions (rank 11–15) mining of river banks make them the include some misconceptions. Some farmers scourge of inland water bodies (Carpe diem

62 Bureau of Rural Sciences Table 7: Problems associated with carp by landholder and angler organisations in New South Wales. The problems are listed in decreasing order of the number of times each problem was mentioned by respondents (P. Gehrke, New South Wales Fisheries, unpublished data 1998)

Problem Rank

Major problem and should be discouraged or eradicated 1 Increase bank erosion by undercutting =2 Increase turbidity =2 Reduce macrophytes 4 Compete with native fish 5 Fishways and other measures needed to help native species compete against 6 carp Disturb bed sediments =7 Activate phosphorus in sediments =7 Reduce native fish numbers =7

Reduce river health =7 Increase frequency of tree collapse =11 Increase nutrient loading =11 Cause poor water aesthetics and dirty water =13 Resource value of carp not fully recognised =13 Increase silting of shallow reaches 15 Widen river channels =16 Overpopulate channels =16 Increase salinity/waterlogging of soil by causing channel leakage =16 Scare livestock from watering points =16 Prevent vegetation regrowth by eating seeds =16 Increase algal blooms by preying on algal grazers =16 Damage wetlands =16

Decrease biodiversity =16 documentary 1998). He believes that envi- efforts will reduce the impacts of carp and ronmental problems caused by carp are improve conditions for native fish. For exam- widespread and include eutrophication of ple, Settlers Creek Landcare Group, in South waters and blooms of blue-green algae. Gippsland Victoria, has implemented a Scientific evidence indicates that carp may restoration project in a small stream as they contribute to these problems under some believe that carp harm aquatic habitats and environmental conditions, but carp alone do may have a negative effect on river blackfish not cause the problems (Section 4.3). (Gadopsis marmoratus). This type of work will help determine whether the presence of Some community groups undertake habitat carp or the lack of riparian vegetation is the restoration projects in the belief that their most important factor in causing instability of

Managing the Impacts of Carp 63 riverbanks and subsequent undermining (W. 4.3 Attitudes of envir onmental Brown, Settlers Creek Landcare Group, authorities in Australia Victoria, pers. comm. 1997) (see case study in Section 8.6.2). Many stream ecologists claim there is no The National Carp Task Force (NCTF) has supporting evidence for claims by landhold- implemented a carp education strategy pos- ers that carp cause bank collapse and topple ing the question of whether carp are really trees (W. O’Connor, Department of Natural the villains they are portrayed as, or rather Resources and Environment, Victoria, pers. are scapegoats for 200 years of inappropriate comm. 1998). There is reliable evidence that river management. The aim is to improve other factors such as uncontrolled stock community awareness of facts about the access (Robertson 1997, 1998) and clearing spread of carp as an introduced fish and their of riparian vegetation (Growns et al. 1998) impacts as well as other factors involved in have had a devastating effect on rivers and degradation of river habitats. Networking of native fish (Sections 2.1.4 and 3.5). Federal those already involved in carp research and and State government natural resources commercial activity is also a high priority. agencies have adopted policies encouraging Myths and misconceptions about carp in better management of riparian zones to Australia, as known by Australian scientists, enhance bank stability. Bank stability is have been summarised in Table 9. Much of essentially a function of the native vegetation the accurate information has not been cover on the banks, and not the presence or spread to the general public (Chapter 9). absence of carp in the stream. For example, the lower Glenelg–Wannon system in In Victoria, the Waterwatch Program includ- Western Victoria has no carp and is severely ed awareness of carp as the main activity for eroded because of over clearing of riparian Water Week in October 1998. Carp fishing vegetation, stock access to the water’s edge competitions have been organised in many and de-snagging. In contrast, the lower areas in New South Wales, Victoria and Ovens River (northern Victoria) has substan- South Australia to raise public awareness. tial carp populations and has stable banks. Community groups are often willing to work This is because there is an intact native ripar- together and to cooperate with government ian forest, abundant instream snags and departments to address a common problem grazing by stock is limited. For these reasons such as carp. The newsletter of the NCTF the Ovens also has the best population of aims to consolidate community energy by Murray cod (Maccullochella peelii peelii) in providing accurate information to all inter- Victoria (W. O’Connor, Department of ested groups. The intention is not to eradi- Natural Resources and Environment, cate carp, but to facilitate carp control Victoria, pers. comm. 1998). through community cooperation. In addition to becoming involved in habitat ‘Water authorities vary in their restoration and carp removal, the communi- attitudes to the presence of carp ty has a valuable role to play in monitoring in channels.’ of water quality and other aquatic ecosystem indicators (Section 8.5.1) and early detection and reporting of the establish- Water authorities vary in their attitudes to the ment of carp populations in new areas. As presence of carp in channels. Their views part of the latter, local communities could range from complacency about the presence erect signs indicating carp-free areas, with a of carp, to seeking funds to reduce their carp diagram and contact phone number to numbers by using them as a commercial allow positive identification and reporting resource. One water authority in Victoria of carp sightings. Such signs would increase believed the changes to water quality caused awareness and community ownership of by carp justified expenditure for their the issue. removal (Section 5.4.4; Box 2).

64 Bureau of Rural Sciences Catchment Management Authorities (CMAs) undertaken in conjunction with other river in Victoria are responsible for managing rehabilitation measures (Roberts and Ebner catchments and water bodies. Included in 1997). their objectives is the development of inte- Control techniques to reduce carp popula- grated strategies for pest animal control by tions favoured by conservation groups government agencies and landholders. The include: Boards that preceded the CMAs published strategies that mention carp as a pest • habitat rehabilitation (Section 7.3.2) because of their detrimental effects in under- including improved river flows (Section mining river banks (A. Roder, Mitchell River 7.4.2) Management Board, Victoria, pers. comm. 1996). While works were underway attempt- • revival of native fish populations to ing to restore river habitats, carp were seen increase predation (Section 7.3.2) to be a threat to stable banks. Some carp control methods may have unde- • genetic or immunocontraceptive carp sirable environmental impacts. For example, control methods (if these techniques one concern is that methods causing rapid become available) (Section 7.3.5 and and high mortality rates could cause tonnes 7.3.6). of putrefying carp in some aquatic habitats (A. Baxter, Fisheries Victoria, Department of Natural Resources and Environment, pers. ‘Management options that offer comm. 1999). long-term solutions, have a sound ecological basis, and which are 4.4 Conservation gr oups complemented by environmental rehabilitation that may enhance native fish populations, are 4.4.1 General opinions favoured.’ Conservation groups in Australia generally see carp as an environmental pest that may Generally, conservation groups prefer con- contribute to undesirable changes to natural trol techniques which cause minimal envi- ecosystems, but recognise carp as a symp- ronmental damage and pose a low risk to tom rather than a cause of major environ- native species. The use of viruses as biologi- mental damage. They consider that carp cal control agents was viewed as dangerous have often been used to divert attention in inland waters because of their potential to away from the real but larger and more diffi- affect native species. Conservation groups cult environmental problems, such as would like the use of chemicals for carp con- reduced river flows and lack of willingness trol to be subjected to environmental impact to finance habitat restoration. Conservation statements (T. Fisher, Australian Conservation groups also view the damage caused by carp Foundation, Victoria, pers. comm. 1998). in the context of damage caused by other Carp control is particularly favoured in areas introduced species such as gambusia of high conservation value, degraded habi- (Gambusia holbrooki), redfin perch (Perca tats, or where endangered species might be fluviatilis), brown trout (Salmo trutta) and affected. Management options that offer rainbow trout (Oncorhynchus mykiss) long-term solutions, have a sound ecological (Tilzey 1976; Fletcher 1986). basis, and which are complemented by envi- Whilst favouring eradication of carp, or man- ronmental rehabilitation that may enhance agement for population control where eradi- native fish populations, are favoured (T. cation is not possible, many conservationists Fisher, Australian Conservation Foundation, believe carp control should be placed well Victoria, pers. comm. 1998). down the list as a priority for river manage- Cynicism was expressed at the prospect of ment. Any carp control activities must be carp control ever receiving comparable

Managing the Impacts of Carp 65 expenditure and support to that spent on NFA would prefer to see carp eradicated fox, rabbit and weed control, given the from Australia but believe carp control apparently smaller effects of carp on agricul- should be considered in the context of other tural productivity. Suggestions were made introduced species which should also be that major river users such as the irrigation controlled. NFA considered the attention industry and anglers should make some con- focussed on carp distracts from the real envi- tribution to control efforts. Anger was ronmental issues such as river flows and expressed at the promotion of coarse fishing habitat rehabilitation. In line with the view of and re-release of carp during coarse fishing conservation groups, NFA considers that the competitions (T. Fisher, Australian cost of carp control should be justified Conservation Foundation, Victoria, pers. against other priority riverine issues. comm. 1998). Rehabilitation of river habitats, in particular flows, was seen as a real solution to the 4.4.2 Professional or ganisations decline of native fish populations. Strong native fish populations could then exert pre- The Australian Society for Fish Biology dation pressure on carp populations and be (ASFB) has a membership of over 600 fish- the most important factor in their control (N. eries professionals and students. The ASFB Thorn, Native Fish Australia, Victoria, pers. considers that carp are an undesirable intro- comm. 1998). duced species and that steps should be taken to control them (D. Pollard, Exotic Fishes NFA considers that the decision by the Sub-Committee representative, NSW, pers. Victorian Government to give permits for re- comm. 1998). The ASFB considers appropri- release of carp by coarse anglers during ate control methods need to be determined competitions (Section 4.9.2) is against the although the harvesting of carp could be principles of carp control. undertaken as an interim measure to reduce numbers in localised areas. Eradication or ‘Carp control should be consid- control techniques should be combined with ered in the context of other habitat rehabilitation to restore the natural introduced species which should balance in favour of native fish species, also be controlled.’ which may then exert competition and predation pressure on carp to help provide a long-term solution. The South Australian Field and Game Association (SAFGA) believe that carp cause damage to wetland habitats of native birds. 4.4.3 Other or ganisations They requested the Murray–Darling Native Fish Australia (NFA) represents up to Association (MDA) to support a forum on 20 000 people through affiliated angling carp (P. Teakle, South Australian Field and clubs. NFA considers that carp are a symp- Game Association, pers. comm. 1995) which tom of degraded rivers and aquatic habitats. subsequently took place at Renmark, South NFA members have witnessed the decline of Australia (Murray–Darling Association 1995). native species which they perceive is caused The group believes that habitats will be by alterations in river flows, altered water restored if carp are removed, so they estab- temperatures and lack of flooding (G. Creed, lished large-scale works to manage the water Native Fish Australia, Victoria, pers. comm. levels and to exclude carp at Pilby Creek, an 1998). The decline of trout cod anabranch of the Murray River near the (Maccullochella macquariensis) has caused South Australian and New South Wales bor- particular concern in many areas. NFA der. The alliances of the SAFGA with other believe that the decline of some native fish groups such as the MDA have resulted in such as freshwater catfish (Tandanus tan- national funding for specific works. The danus) and silver perch (Bidyanus results, described in Section 8.6.1, Box 9, bidyanus) may be caused by carp competing demonstrated that in the absence of carp for food. aquatic vegetation became abundant.

66 Bureau of Rural Sciences 4.5 Indigenous communities the environment. They have to modify their culture because of environmental changes Members of some indigenous communities such as the introduction of carp. This is not a hold strong opinions on the need to ‘get rid universal belief amongst Australian of carp’ (M. Morgan, Yorta Yorta community, Aboriginal peoples. For some, abundance is Victoria, pers. comm. 1998). Community more important than diversity, so that these elders of the Yorta Yorta community have people do not necessarily distinguish observed changes to habitats, native fish between native and introduced species numbers, bird habitats and bird breeding (Tilmouth 1995). areas which they attribute to the introduction The role of the irrigation industry in reducing of carp along the Murray River in New South flows in the Murray River is seen by some Wales and in the Barmah Forest. Elders indigenous peoples as a major factor con- expressed a great desire for eradication or tributing to the decline of native fish popula- ‘total control’, and showed interest in tions and the increase in carp (M. Morgan, becoming involved in such efforts if this Yorta Yorta community, Victoria, pers. were possible. Few people from indigenous comm. 1998). The lack of seasonality in the communities known to the Yorta Yorta have drying and flooding of wetlands provides used carp as food and generally they just carp with extensive permanent spawning ‘chucked them on the bank’. and rearing areas. ‘A decline in the environment may Control methods are readily sought, be equated with a decline in the although the Yorta Yorta people are con- standards of indigenous culture cerned at the possibility of further biological introductions or controls which have no and community.’ guarantee of not having adverse effects on native species. This concern is heightened Along the Darling River, New South Wales, by the history of the effects of viruses and various indigenous communities have wit- other diseases introduced to Australia by nessed the increase in numbers of carp (V. Europeans and the devastating effects they Crawford, Waterwatch Facilitator for indige- had on indigenous people. nous people of the Darling catchment, Strong concern was also expressed at the Bourke, NSW, pers. comm. 1998). possibility of the development of carp har- Indigenous communities along the Darling vesting as an industry which could be seen regard carp as a problem because they have as sustainable, as this may in turn hinder replaced valued populations of native fish. their eradication because of the effect on A unique effect of carp on indigenous peo- investment and livelihoods of those involved ples is the influence on their culture. As laws in a carp industry. If population control and cultural conditions are often related methods were to be implemented potential closely to the land and the environment, litigation or compensation claims could changes to that environment cause changes occur – for example, complaints from the to traditional, laws, customs and traditions. rabbit industry following the release of con- This leads to a loss of many of these trol viral agents (M. Morgan, Yorta Yorta attributes (M. Morgan, Yorta Yorta communi- community, Victoria, pers. comm. 1998). ty, Victoria, pers. comm. 1998). Some indige- Commercial harvesting of carp is seen to nous people see both themselves and biodi- raise several other concerns including: versity as mutual and important components of the environment. Therefore, a decline in • risk of injuries to non-target native the environment may be equated with a species by capture techniques decline in the standards of indigenous culture and community. This is in contrast to the • illegal capture of native species European view of using the environment rather than being part of it. The indigenous • insufficient reduction of carp popula- community see themselves as protectors of tions to reduce damage

Managing the Impacts of Carp 67 • diversion of attention from other under- • There is a significant qualitative differ- lying environmental problems and the ence between the humane management promotion of carp harvesting as a solu- of species in large numbers which tion to the carp problem. threaten a system’s environmental and ecological balance and a public call for Changes to flow regimes, environmental extermination of the same species. rehabilitation and removal are all favoured There may be a tendency to exaggerate as control options. There is also strong sup- damage done leading to unchecked cru- port for further research, particularly into elty in killing practices. This calls for breeding patterns, so that management deci- innovative strategies for population con- sions can be made with better understanding trol or humane euthanasia of individu- (M. Morgan, Yorta Yorta community, als. Victoria, pers. comm. 1998). • Placing a bounty on the head of a pest species by means of commercial 4.6 Animal welfar e and animal exploitation will create a commodity of rights the species and lead to greater excesses in their harvesting. It may well become a Animal welfare organisations aim to protect self-defeating control strategy if an animals from cruelty and unnecessary suffer- industry arises around carp control that ing. There are a variety of opinions from demands continual supply of stocks these groups in relation to the killing of ani- (Section 7.3.1). mals as a control option. Generally animal welfare groups have a preference for control • All species evolve when new resident methods which do not kill animals or cause species adapt to each other. Strategies animal suffering. Attitudes to killing fish are should aim to restore a level of balance. sometimes, although not always, less stringent than those expressed against killing • Angling, harvesting (commercial or sci- larger terrestrial animals. entific), viral, chemical and molecular Some general principles adopted by animal control options were rejected for being welfare groups include: inhumane and for having potential detri- • avoidance of pain or suffering if at all mental impacts on non-target species. possible • A contraceptive approach was consid- • the use of humane killing methods ered to provide the most humane control option, perhaps in combination with • targeted actions which do not adversely mechanical control strategies such as affect other species environmental manipulation or exclusion as long as these did not threaten • the need to demonstrate planned man- the well-being of existing carp but acted agement. to reduce numbers over time. Similarly, predator stockings would be acceptable if this did not result in a ‘cane toad’ 4.6.1 Animal rights and animal effect with the resultant need to control liberation or ganisations the predator.

Opinions given by a campaign coordinator The basic premise of most animal rights for Animal Liberation (R. Linden, Animal organisations is that no animal’s interests are Liberation, Victoria, pers. comm. 1998) sug- served by it being killed. Animals should gest that: only be killed if there is some reason which is thought to override the animal’s interests

68 Bureau of Rural Sciences (Russell and Pope 1993). Some recreational comm. 1998). Only one operator, K&C fishers who regard themselves as coarse Fisheries in the Gippsland Lakes, currently anglers also hold this belief and prefer to makes a living from carp (Section 5.4.3). release carp alive (Section 4.9.2). K&C Fisheries managers consider that the only way to profit from carp harvesting is to use methods of capture and quality handling 4.7 Commer cial fishing industry that ensure a high-grade product goes to fish markets. There is a range of attitudes within the carp commercial fishing industry. Many perceive A South Australian commercial carp harvester carp as a potential source of quick money believes that the food chain has been affect- because of the large numbers present in ed by carp to the extent that native fish such many places. A commercial seine operator in as silver perch, freshwater catfish, congolli New South Wales (Carpe diem documentary (Pseudaphritis urvillii) and yabbies (Cherax 1998) has moved from the coast, where com- destructor) have probably decreased (Jones mercial fishing is declining, to northern New 1995). Human disturbances such as locks, South Wales to establish a carp fishery. He barrages, pollution, river traffic and fishing believes that harvesting carp for human con- have also contributed to the decline of native sumption will yield better money than the fish. Jones (1995) considers that carp num- coastal fishery and has spent two years set- bers could be controlled by commercial fish- ting up this potential business. ing if there were sufficient markets. An operator on the Murray River sells carp to ‘The only way to profit from carp the South Australian crayfish industry as bait harvesting is to use methods of (Section 5.4.1) but this is not a constant mar- capture and handling that ensure ket and he sees the need for an enhanced a high-grade product.’ industry with alternative markets for other times of the year (S. Hounsell, Commercial Fisherman, Swan Hill, Victoria, pers. comm. Most inland commercial fishers support the 1997). eradication of carp, which they view as a low-value nuisance fish that damages gear R. McFarland (Lachlan River Management used for harvesting high-value native Committee, NSW, National Carp Summit, pers. species. Very few commercial licence hold- comm. 1995), who is a carp fertiliser proces- ers currently target, or make most of their sor, believes that government assistance income opportunities from, carp. Many com- should be given to harvesting and processing mercial fishers consider that both rivers and of carp. He considers that it is widely accepted native fish populations would be better off that carp are a huge ecological problem to the without carp. The use of chemicals and viral quality of inland waters and that further scien- agents are not favoured because of possible tific studies on their effects are not warranted. effects on native species. All other control Incentives for the carp industry would drive an options are viewed as possible, including increase in harvesting which he believes harvesting using seine nets and electrofish- would reduce carp populations and the dam- ing. The best carp control options are seen to age caused by carp. The National Carp Task be: long-term solutions which promote Force recognises that commercial exploitation native fish species, including the provision has a place in managing the numbers and of fishways; restoration of environmental impacts of carp and supports the economic flows at the appropriate times of the year; development of commercial operations for and habitat rehabilitation (Chapter 7). carp at a regional level to reduce damage (L. Broster, National Carp Task Force, South Carp have moved further into the Gippsland Australia, pers. comm. 1999). lakes in the past ten years (Section 2.2.2) but are not commercially viable for most fisher- The New South Wales Department of men (A. Allen, East Gippsland Estuarine Regional Development (Carpe diem docu- Fisherman’s Association, Victoria, pers. mentary 1998) encourage and facilitate the

Managing the Impacts of Carp 69 commercial use of carp. They believe a carp tourist dollars than those targeting carp. harvesting industry will generate jobs and Many angling clubs travel in groups to areas help to protect the environment. to target native fish in warm waters and to target trout in cool waters. Not many anglers East Gippsland Shire and the East Gippsland spend money in travel, accommodation and Coastal Board were the innovators in form- tackle to catch carp. This contrasts to atti- ing a network for stakeholders to share infor- tudes in Britain where recreational carp fish- mation to define the extent of damage ing is highly regarded and a valuable indus- caused by carp and to work strategically in try (Section 1.2). In Tasmania, the threat making management decisions (M. Rankin, posed by carp to the valuable trout fishery is East Gippsland Coastal Board, Victoria, pers. a major economic consideration (Section comm. 1997). 6.3.5). There is a difference in opinion between In Victoria 87% of anglers presently target states as to the potential use of large num- introduced trout (Salmonidae) and redfin bers of carp removed from inland waters perch while about 7% target carp, sometimes during recreational fishing competitions. In because of a current lack of opportunities to Gippsland, Victoria, the commercial sector catch native fish (A. Baxter, Fisheries believes that the carp brought in by competi- Victoria, Department of Natural Resources tions are of poor quality and unusable by the and Environment, Morgan omnibus polls markets. At a series of competitions organ- 1996–98, pers. comm. 1999). Consequently ised by the Gippsland Lakes and Catchment the tourism industry is dependent on these Action Group during 1996–98 (Section 4.9.2) introduced species. If carp were to threaten carp could be put in ‘carp only’ rubbish bins the trout, redfin and native fish fisheries this emptied by the East Gippsland Shire and would affect the tourism industry to a greater taken to a landfill area. In South Australia, degree than any reduction caused to angling the commercial and recreational sectors have activity that would occur if carp numbers agreed that commercial fishers will process were controlled. Substantial amounts of carp taken during fishing competitions for money are spent on fishing tackle. Fisheries cray bait or other markets. The aim was to Victoria is stocking Murray cod, golden add value for carp in South Australia rather perch (Macquaria ambigua), silver perch, than producing landfills of buried carp Macquarie perch (Macquaria australasica) (Pierce 1996). A network meeting of com- and bass (Percichthyidae) as well as raising mercial stakeholders from Victoria, New the profile of native fish to maintain recre- South Wales and South Australia was held in ational angling. 1998. They believed that carp harvesting as a control measure should be managed accord- High quality, potable water is important for ing to established fishing industry business tourism and aquatic recreation. A major principles and not an ad hoc community tourist attraction in eastern Victoria is the exercise or one-off control for a pest (G. Gippsland Lakes. If tourists perceive that Gooley, Marine and Freshwater Resources carp are having a detrimental effect on water Institute, Victoria, pers. comm. 1998). quality, the Regional Tourism Board will support applied research into carp (R. Fordham, Gippsland Regional Tourism 4.8 Other businesses Board, Victoria, pers. comm. 1997). Other Chambers of Commerce in rural New South 4.8.1 Tourism Wales believe carp are linked to declines in local tourism business and may support ven- The damage caused by carp, and tourists’ tures to control or eradicate carp. perceptions of water quality, can have a negative effect on tourism businesses such as 4.8.2 Aquacultur e accommodation and services (Section 5.2.1). The tourism industry believes that anglers The value of carp as a display and ornamen- targeting native species will bring in more tal fish is recognised by the Koi Society of

70 Bureau of Rural Sciences Australia. The brightly coloured Koi are bred 4.9 Recr eational fishers on farms and have been highly valued worldwide since the 1930s (Copperfield 1987; Section 1.2). There are many clubs of 4.9.1 Recr eational fishing gr oups enthusiasts for breeding and keeping Koi Many recreational fishers consider carp to be carp especially in New South Wales. an unwanted pest species and they often Koi can only legally be bred in some States blame carp for the declines in the populations (Table 13) and cannot legally be imported of other recreational fish species. Carp are from overseas (Section 6.2). In Victoria, it is believed by some groups to be the most signif- illegal to keep Koi carp and potential enthu- icant factor affecting recreational fishing (G. siasts believe that the State should have less Creed, RecFish (formerly Australian restrictive laws to match other States and Recreational and Sport Fishing Territories. Confederation), Victoria, pers. comm. 1995). Many groups believe that carp compete with Koi carp breeding in the aquarium industry popular angling species for space and food. In produces many thousands of small carp. New South Wales, the Recreational Anglers There are reports the fish are sorted to Association (RAA) believe that carp exclude remove low value juveniles and these may native fish from their preferred habitats (S. be being released into aquatic habitats (G. Ryder, Recreational Anglers Association Robertson, Fisheries WA, pers. comm. 1999). spokesperson, NSW, pers. comm. 1998). The There is a need to regulate the disposal of Victorian Recreational Fishing Peak Body these unwanted carp. (VRFish) perceives carp as a pest species (R. Carp have too low a value for human food to Page, Executive Officer VRFish, Victoria, pers. be suitable for high volume commercial comm. 2000). The policy of VRFish regarding aquaculture in Australia. If a high price for carp in Victoria is: carp was attainable an export market would be possible (K. Bell, K&C Fisheries, Victoria, ‘Many recreational fishers blame pers. comm. 1997). Some believe that if wild carp for the declines of other harvested carp were to become a viable recreational fish species.’ export industry there might be a need to have a supporting aquaculture industry of carp kept in a controlled environments (G. ‘Eradication is not viewed as possible by this Gooley, Marine and Freshwater Resources organisation and commercial harvesting Institute, Victoria, pers. comm. 1998). should be undertaken to use carp as a substi- tute for pilchards and Australian salmon in The technology of intensive carp aquacul- uses such as pet food. The removal of their ture is well known worldwide (Section 1.2), noxious status is suggested as a mechanism and if this could be undertaken in an envi- to enhance their marketability. Carp are ronmentally sensitive and secure way, there viewed as a national problem in need of a may be several opportunities such as the national coordinated solution. Removal of integration of carp production into wastewa- carp by commercial fishing and angling are ter treatment systems and their use and pro- supported as control options, as are duction in rice fields could have economic immunocontraception and genetic manipu- benefits for wastewater use and integrated lations providing there are no threats to the farming practices. Carp are also a low cost environment. Use of poisoning and viral source of pet food which could replace agents is not favoured.’ declining wild fishery products (Newman 1998). If a genetic control technique were There is an expectation by many angling developed for carp there might be a need for groups that removal of carp would improve carp aquaculture to breed up genetically the quality of water and aquatic habitats. modified stocks (Newman 1998). Experiments such as Pilby Creek (Section 8.6.1) led the Far West Anglers Association (FWAA) to believe that carp are the main

Managing the Impacts of Carp 71 Coarse angling is a pastime which values large fighting fish including carp. Source: A. Toovey, NSW Fisheries.

cause of bank degradation, turbidity, water and an implication from this is that carp quality and riparian vegetation degradation (C. should be used for commercial fishing and Mansell, National Carp Summit, Renmark, by anglers. RAA support a carp industry to South Australia, pers. comm. 1995). Their atti- remove large numbers of carp to allow the tude, therefore, is that no more money should return of native fish. Very few anglers use be spent on carp research but rather on con- carp for food and in some States and trol of carp. Territories where it is illegal to return carp to the water alive, anglers often bury carp or ‘There is an expectation by many leave them on river banks. angling groups that removal of The issue of declining habitat because of carp would improve the quality poor catchment management is seen as cen- of water and aquatic habitats.’ tral by some angling clubs and other recreational groups. These groups recognise that the persistent multiple impacts of catchment Most recreational fishing groups and individ- use are such that the removal of carp alone is uals see carp as a problem and want them unlikely to trigger a resurgence of native removed. Opinions differ as to whether this species. removal is the responsibility of government agencies, commercial operators or individuals. RecFish states that carp are good eating,

72 Bureau of Rural Sciences 4.9.2 Carp as a tar geted r ecr eational been exploited and believe that the industry catch for recreational carp fishing that has grown in the United Kingdom could be mirrored in The term ‘coarse fishing’ was coined in Australia. England to distinguish it from the so-called In fishing competitions held in Canberra in ‘gentleman’s sport’ of angling for salmonids 1999, a total of 3600 kilograms of fish were (Salmonidae). The term ‘coarse’ may come removed by 50–70 anglers over four days from the English phrase ‘in-course’ meaning and were then released back into Lake ordinary as it meant all fish that were not Burley Griffin. At least 95% of these fish were salmonids (Clements 1988). ‘Coarse fish’ carp, which is an average of nearly 15 kilo- include the cyprinids roach (Rutilus rutilus), grams of carp per angler per day (Lintermans rudd (Scardinius erythrophthalmus), chub 1999). (Leuciscus cephalus) and dace (Leuciscus leuciscus) (see also Table 1). Coarse fishing In contrast to activities by the coarse anglers, has a long history, being undertaken for food the FWAA believes that catch-and-release of by Europeans, and eventually becoming a carp should be illegal (C. Mansell, Far West popular recreation in the United Kingdom Anglers Association, Victoria, National Carp and other countries. A more recent philoso- Summit, pers. comm. 1996). Other anglers phy of coarse anglers is to practice catch- believe their attempts to increase the survival and-release of live fish. In Europe, carp up to of native fish are hampered by coarse 20 kilograms are caught using bait and bur- anglers returning carp to the water (G. ley through a variety of techniques. The Creed, Native Fish Australia, Victoria, pers. sport is also growing in the United States of comm. 1998). Concern has also been America. expressed by many anglers about the deliberate transfer of carp to new waters to estab- Coarse fishing clubs in Australia now exist in lish new coarse fisheries. New South Wales, the Australian Capital Territory, Victoria and South Australia. A group in Australia called the Australian ‘A more recent philosophy of Federation of Coarse Anglers Association coarse anglers is to practice (AFCAA) have a policy of catch-and-release catch-and-release of live fish.’ of carp (B. Dimmack, Chair Australian Federation of Coarse Anglers Association, The attitude of coarse anglers is that fishing Victoria, pers. comm. 1998) which is contro- is a sport with a need to respect the fish as an versial (Section 4.4.3). In one competition animal. Some believe that it is cruel to tether held in March 1998 between 18 Australian carp and to leave carp to die (S. Roberts, and New Zealand teams, a total of 605 kilo- member of Sydney Coarse Angling Club, grams of carp were caught in 12 hours in the NSW, pers. comm. 1998). Some coarse Barwon River in Victoria. All carp were anglers are upset at the needless and cruel returned to the water alive under a special death of many carp and believe that this dis- permit issued by Fisheries Victoria that allow respect has resulted from widely held views participants in AFCAA events to hold live that carp are villains that have caused all the carp and return them within 10 metres of the catchment problems (B. Waldock, Australian point of capture. (A. Baxter, Fisheries Federation of Coarse Anglers Association, Victoria, Department of Natural Resources Victoria, pers. comm. 1998). and Environment, pers. comm. 1999) (Section 6.3.1). The specified waters in Some angling clubs promote carp as an inter- Victoria for 1998 to 1999 also included the esting target species because of their fighting public waters of Lake Eildon, Yarra River, abilities and also encourage people to fish for Maribyrnong River and Eummerring Creek. carp as a removal measure. A member of the The Hazelwood Pondage close to the site Johnsonville Angling club has supported the where Boolara carp were first released in Gippsland Lakes and Catchment Action Gippsland is also a site for AFCAA events. Group in running a continuous two-monthly AFCAA see carp as a resource that has not competition. Prizes are given for a mystery

Managing the Impacts of Carp 73 fish in each competition to encourage people $1.25 per kilogram (Carpe diem documen- to bring in all fish caught. As most carp tary 1998). Carp sold at the Victoria Market, would not be consumed a waste bin is pro- Melbourne, have fetched up to $1.50 whole- vided. The club also aims to contribute to sci- sale per kilogram since commercial catches entific data and for this purpose records the began in 1970s (Section 5.4). Retail prices for measurements of all carp caught. carp are usually $4–$6 per kilogram. The range of carp food products has ‘Some angling clubs promote increased in the last five years and many carp as an interesting target recipes for cooking carp may be found in species because of their fighting newspaper columns, fishing magazines and abilities and also encourage recipe books. The aim of many such publica- people to fish for carp as a tions is to raise awareness of carp as a seri- removal measure.’ ous environmental problem which people can help solve by removing carp and eating them (Easton and Elder 1997). A view held by some recreational fishers is that there is no reason to go fishing anymore 4.10.2 Export markets because all they catch is carp, and they do not like to eat carp (C. Easton, NSW Positive attitudes held in many European Department of Land and Water Conservation, and Asian countries towards consumption of pers. comm. 1999). Some groups are attempt- carp may offer export opportunities. One ing to change such attitudes. In 1996, the Australian operation currently exports to Executive Director of the South Australia Poland (Section 5.4.2). K&C Fisheries aims to Recreational Fishing Advisory Council report- export $5 million worth of carp each year for ed on the recreational possibilities of carp human consumption in Europe (Ashley- fishing (Winwood 1996). He suggested that Griffiths 1998) (see also Section 5.4.2). carp fishing can be enjoyable and that burley However, most potential importers are cur- and bait can be used to successfully catch rently offering prices that are too low to sup- carp, especially if light gear is used. port a profitable Australian export industry.

4.10 Carp for human 4.11 Carp action gr oups and catchment management consumption The first major forum for public discussion on carp was in Wagga Wagga in June 1994 4.10.1 Local markets (Murrumbidgee Catchment Management Carp are high in protein, nutritious, and in Committee 1994). In 1995, a two-day forum the opinion of many people in Europe and on carp was held in Renmark. It was organ- Asia, tasty to eat. Most Australians, however, ised by the Murray–Darling Association and either regard the fish as a poor quality food, was seen to be a Summit following a series because of its low price, or believe that carp of similar workshops (Murray–Darling are unsuitable for eating. Usually only peo- Association 1995). The proceedings of the ple of recent European or Asian origin pur- forum reflected the opinions of various chase carp for food in Australian markets. stakeholders. One outcome was the forma- The noxious status of carp and the belief that tion of the National Carp Task Force (NCTF). they are taken from muddy or even polluted The aim of the NCTF was ‘to eradicate carp waters may have influenced perceptions from all Australian inland waters through a held by some people. The sale of carp for coordinated action plan that promotes coor- human consumption is limited, even when dinated research, provides good informa- the carp are of high quality. Hence carp are tion, explores commercial opportunities and one of the cheapest fish because of low seeks complementary legislation’ (National demand. Carp sold at the Sydney Fish Carp Task Force 1996a; Section 6.2.1). Markets currently total 110 tonnes per year and fetch an average wholesale price of

74 Bureau of Rural Sciences A total catchment approach was taken by the River Basin Management Society Incorporated. At a forum for algal and nutrient management in 1995, carp were seen to be less of a problem than turbidity, bluegreen algae (Cyanobacteria), river regulation, water quality, catchment degradation and other introduced species (McNee 1995). The philosophy underlying this approach was that carp should not be the scapegoat for other river problems and that the community perception needs to recognise that carp are part of a bigger problem of poor land and water management. Community perceptions often focus only on the physical presence of carp.

‘Carp control is unlikely to rectify all apparent problems.’

Many action groups and those that come together at forums (Section 6.1) feel that the general public is unaware of the serious threat to aquatic systems posed by carp. Most groups mention at least one other factor affecting aquatic environments, such as altered water flows and increase in nutrients. Less likely to be mentioned are presence of cattle, land clearing, removal of streamside vegetation, previous decline of native fish, removal of instream habitats for native fish and the creation of still water habitats. There may be agreement that nutrients have increased but whether this is from agricultural fertilisers, cattle or urban effluents and run-off may vary with the locality. It is widely assumed by catchment action groups that efforts to reduce factors that degrade river health (such as altered flows, land clearing, and nutrient increases), will help reduce catchment problems that are sometimes attributed to carp. If carp control is implemented it will be important to monitor changes in river health (particularly aquatic plants, native fish, turbidity and bank erosion) to determine if the expected benefits are realised (Section 8.5.2). Carp control alone is unlikely to rectify all apparent problems.

Managing the Impacts of Carp 75

5. Economic and envir onmental impacts and commer cial use

Summary these effects appear to be site specific and the mechanisms are not well understood. Carp can inflict major economic and environmental costs on both the public and pri- Much of the commercial carp catch is sold vate sectors by reducing water quality and for low price uses such as crayfish and lob- degrading aquatic habitats. Industries ster bait and fertiliser. There is currently little which are affected include water suppliers human consumption of carp in Australia for domestic and industrial users, agricul- and any value-added products are currently ture, commercial and recreational fisheries only produced on a small scale. and tourism. Although carp are often Commercial harvest is only seen as con- regarded as having a harmful effect on tributing to the control of carp in certain aquatic habitats, there has been little quan- areas and is unlikely to achieve wide-scale titative evaluation of the damage they cause population reductions. to either the economy or the natural envi- Carp are perceived negatively by most ronment in Australia. The distribution and anglers because they are not popular for abundance of carp, and their dominance of angling or eating. Angling is one of the most fish communities across their range is well- popular recreational sports in Australia and described on a large scale, but their status in the dominance of carp in many fish popula- many individual sub-catchments is uncer- tions has potential to reduce angler partici- tain. There are also important knowledge pation, particularly where numbers of pre- gaps about the biology of carp under ferred native fish species are low. Declining Australian conditions and their impacts on angler participation could cause substantial Australian aquatic ecosystems. losses to fishing supply and associated Although many of the potential impacts of tourist industries. However, ‘coarse angling’ carp have received some study both in for carp is gaining popularity. Australia and overseas, the scale of many of the impacts is not clear because they can also 5.1 Intr oduction be caused by other factors. Evidence exists for increases in water turbidity in the presence of In order to predict the benefits of reducing carp, although the extent appears to be site carp (Cyprinus carpio) to lower densities, specific. This increase is partly caused by the there is a need to understand and quantify resuspension of sediments when carp feed. the damage they cause at a range of densi- Their method of feeding is also responsible for ties, so that managers can determine the destruction of many aquatic plants, espe- whether the benefits of control justify the cially those with soft stems and shallow roots. costs. The impacts of carp need to be consid- There is some evidence that carp cause elevat- ered in relation to information given in other ed nutrient concentrations. Impacts on sections, especially those relating to their native fish fauna are less well documented control (Section 7.3) and to other influences even though carp now dominate many fresh- on the natural environment (Section 3.5). water fish communities. Declines in native fish populations in many areas had already No study has been undertaken to quantify begun prior to the expansion of carp and so any economic effects, and although the envi- the specific impacts of carp are difficult to ronmental effects of carp have been widely ascertain. It is probable, however, that the debated, there have been few controlled sci- reduced abundance of native fish species entific studies to quantify these effects and aided the establishment of carp. Changes in few attempts to extrapolate any impacts macroinvertebrate populations have throughout the range of carp in wetland or occurred following the expansion of carp but river habitats (King 1995).

Managing the Impacts of Carp 77 5.2 Economic impacts sediment loads, increased nutrient concentrations and algal densities which can clog Economic impacts of carp could impose water delivery machinery, such as pumps major costs on both the public and private and filters, and increase pump wear and the sectors. As most waters are ‘owned’ or con- cost of water treatment. Other costs caused trolled by government agencies, most costs by the impacts of carp on the agricultural associated with carp control would be borne industry could include damage to river by government. Some of these costs may be frontages (Section 4.2) and loss of water passed on to water users. There is a need to quality for cattle. However, as most of these assess the economic and social costs of carp, impacts are also caused by factors other than the likely benefits of implementing control carp, it is difficult to apportion the costs and the costs of damage where control is directly attributable to carp. minimal. Analyses of the costs and benefits Recreational fishing is one of the most popu- of carp control are needed on both a local lar participator sports in Australia and sup- and regional basis and for different types of ports an industry worth millions of dollars economic damage inflicted by carp. Impacts per annum. The contribution of the recre- on the environment also need to be consid- ational fishery (including support industries) ered if no carp control is undertaken. to the Victorian economy is estimated to be To date, control or eradication of carp has about $1.3 billion per annum and generates only been attempted on a local scale with about 27 000 jobs, although inland fishing relatively little government expenditure. accounts for less than 25% of this (Unkles There has been no analysis of economic 1997). To date only a small proportion of losses associated with carp and no economic anglers actively seek carp and this is largely assessments of reduced damage as a result of restricted to specialised ‘coarse’ anglers who localised carp control. follow European traditions including catch and release. Some ethnic groups selectively 5.2.1 Impacts on industry fish for carp for human consumption. A recent survey of recreational fishers in Carp have potential to increase costs to sev- Victoria reported that in 1996 only 6.7% of eral industries including: freshwater anglers sought carp as a preferred species (Unkles 1997). This figure is expect- • domestic and irrigation water suppliers ed to include some anglers who realistically assumed that carp was the species they • agriculture could expect to catch and, given a choice, they would prefer other species. There are • recreational fisheries no comparative figures nationally, although given the ethnic mix of the Victorian popula- • commercial fisheries tion and the widespread availability of carp in comparison to other native species, any • tourism. preference for this species in Victoria is likely to be higher than the national average. It has been suggested that carp may be a sig- Reductions in angling participation caused nificant cost to the water industry because either by angler attitudes to carp or by carp- when they feed by sifting through the sub- induced reductions in native fish popula- strate they cause erosion and slumping of tions would have significant negative flow- irrigation delivery channels (Eagle 1994; on effects to the tourist industry. Particular Jackel 1996; Section 4.2). Although repair to concern has been expressed in Tasmania, irrigation channels through bank stabilisa- where the image of a high quality trout fish- tion works is a substantial cost, these prob- ery has been tainted by the introduction of lems are unlikely to be caused solely by carp carp. During the enforced closure of and other factors are probably more signifi- Tasmanian lakes containing carp, some local cant causes (Section 4.3). Other problems economies were badly affected (A. Sanger, attributed to carp are increased suspended

78 Bureau of Rural Sciences Tasmanian Inland Fisheries Commission, Hemisphere ecosystems where carp have pers. comm. 1997). Costs to the tourist indus- been more intensively studied. For this rea- try and the revenue of Tasmania have not son, it may be inaccurate to extrapolate any been assessed but licence figures have not conclusions drawn from overseas studies to shown a decline since carp were discovered Australian conditions. (W. Fulton, Tasmanian Inland Fisheries Table 8 indicates that impacts of carp are Commission, pers. comm. 1998). In an analy- hard to establish in riverine systems, and sis of the effects of carp in the Gippsland many impacts have been inferred from stud- Lakes in Victoria, it has been estimated that ies in wetlands. the costs to the community over five years are $175 million (Gippsland Lakes and There is considerable discussion and anec- Catchment Action Group 1996). This includ- dotal evidence as to the environmental ed losses to the native commercial fishery impacts of carp and a considerable number and losses to recreational fishing, tourism of perceptions which have little or no basis. and commerce. Mechanisms for these losses Whilst the facts as known to Australian scien- were not explained. tists are outlined in Sections 1 – 3, Table 9 provides a summary of some common pub- ‘Reductions in aquatic plants, lic perceptions compared to scientific facts. increased turbidity and effects There is little Australian research quantifying on recreational fishing may all the impacts of carp on various ecosystem reduce the tourism potential of components. Major projects which have an area.’ been completed include: the Victorian Carp Program undertaken from 1979 to 1982 (Hume et al. 1983b; Fletcher et al. 1985); Potential negative impacts of carp on recre- some farm dams (Malcolm 1971); billabong ational fishing for desirable species is likely and pond experiments (Robertson et al. to be substantial. In contrast, any gains from 1995; Roberts et al. 1995; King et al. 1997); anglers actively seeking carp are likely to be studies of irrigation drains (Bales 1994; localised and minimal. Any impact of carp Bowmer et al. 1994; Meredith et al. 1995); on native commercial fisheries could cause and rivers (Driver et al. 1997). There are significant commercial losses although such unpublished studies which have investigated impacts have not been quantified. Because the effects of carp on plant communities (J. carp create a negative environmental image Swirepik, unpublished data, 1998). Most of for some people (Chapter 4), waters with these studies focus on water quality issues. high carp numbers which are readily visible can be viewed as ‘degraded’. This perception, together with reductions in aquatic 5.3.1 Difficulties assessing, plants, increased turbidity and effects on assigning and valuing recreational fishing may all reduce the envir onmental damage tourism potential of an area. A key difficulty in assessing environmental costs is determining the actual environmen- 5.3 Envir onmental impact tal effects caused by carp. Figure 12 illustrates some of the direct and indirect impacts The effects of carp overseas were reviewed that carp may have on environmental vari- by Fletcher (1979), King (1995) and Roberts ables. Many of the potential effects of carp and Ebner (1997). Although environmental could also be caused by other factors and impacts of carp have not been well studied because causal links are often unclear, quan- in Australia, similar detrimental effects on tification of the potential damage has not aquatic plants and increases in water turbidi- been attempted. This makes it difficult to ty have been attributed to carp (Table 8; assess environmental damage. King 1995). Australian aquatic ecosystems Even if the negative effects of carp on the differ substantially from temperate Northern natural environment and native species were

Managing the Impacts of Carp 79 Table 8: Summary of supporting evidence for suggested impacts of carp in aquatic habitats. Point scale: * anecdotal evidence only, ** survey and/or dietary studies, *** artificial and tank experiments, **** field experimental studies (adapted from King 1995).

Location Habitat type Still water (lentic) River (lotic) a. Overseas studies Turbidity **** * Macrophytes **** * Macroinvertebrates **** * Phytoplankton concentrations **** * Interactions with native fish * * Stream bank erosion * * Nutrient concentrations *** *** b. Australian studies Turbidity **** ** Macrophytes **** ** Macroinvertebrates **** * Phytoplankton concentrations **** * Interactions with native fish ** ** Stream bank erosion * * Nutrient concentrations **** * well described and quantified, assigning have only recently moved beyond the initial value would be difficult. While there are stage of identifying interactions and into the methods for estimating the cost of environ- further stages of description and measuring. mental damage, they are generally not uni- Few studies have been undertaken on the versally accepted (Braysher 1993). An assess- effects on ecosystems and therefore an over- ment of the impact of pest fish species is, in all assessment of impacts is not possible at effect, an ecological analysis of the nature present (Roberts and Ebner 1997). These and results of interactions between the pest issues of scale often mean that the impacts of and native fish species and their habitats carp can be obscure and difficult to ascertain (Taylor et al. 1984) or other components of (Driver et al. 1997). their environment. Research must progress through the stages of: 5.3.2 Erosion • determining which interactions occur Jackel (1996) made anecdotal observations on the effects of carp ‘causing’ erosion to the • describing and measuring them banks of irrigation channels but these were not extrapolated to river systems. Many land- • determining their significance. holders also believe that carp in channel and river systems are causing damage to banks Assessing the significance of interactions (Eagle 1994; R. McFarland, Lachlan River gra- requires extrapolation across temporal and zier, NSW, pers. comm. 1998; Section 4.2). spatial scales and relies on designed experi- Roberts and McCorkelle (1995) investigated mental studies, usually conducted in more the role of carp in channel bank erosion by than one location. In Australia, such studies excluding carp from sections of bank over the nine month irrigation season.

80 Bureau of Rural Sciences Table 9: Common perceptions versus facts about carp in Australia.

Common perceptions Scientific facts Carp spawn every year Carp do not necessarily spawn or successfully recruit every year Carp lay millions of eggs Carp are very fecund and can lay millions of eggs per year Eggs are spread by birds feet and are able to Carp eggs only survive out of water for a short time survive in mud and in the water to be fertilised at and are usually attached to plants (Adamek 1998; any time Section 3.4.2). Unfertilised eggs soon die

Carp can survive in seawater Carp cannot survive in seawater but are tolerant to half seawater salinity Carp can swim away and survive even after they Carp may swim away using reflex actions but have been cut open almost certainly die later Carp stay alive in mud Carp cannot live in mud Carp undermine river banks Carp feed by sifting through mud but there is no evidence that they undermine river banks Carp cause trees to fall into rivers There is no evidence for this Carp damage aquatic plants Carp uproot soft-leaved plants (Fletcher et al. 1985; Roberts et al. 1995; Section 5.3.5) Carp spread diseases A large number of parasites, diseases and viruses (Sections 5.3.7 and 3.4.4) have been associated with carp but there have been no specific reports of deaths of native fish caused by carp-borne diseases in Australia (Roberts and Ebner 1997)

Carp flesh is not good food Carp flesh is nutritious and can be eaten and refined into many fish products for human consumption Carp eat native fish and eggs Carp may eat small numbers of eggs or larvae of certain species but these are likely to be taken incidentally and is unlikely to reduce populations of these species

Undercutting and bank slumping was 5.3.3 Water quality observed to occur, in all sections studied, including where carp were excluded, and so Many of the effects of carp on water quality these effects could not be attributed to carp. can be related to their feeding behaviour This highlights one of the problems in isolat- (Section 3.3.1). Carp feeding activity increasing the effects of carp from other effects such es turbidity by continually resuspending sed- as high flows, excessive water extraction, iments. Both overseas and Australian studies lack of riparian vegetation and livestock demonstrate increased turbidity in the pres- access, which can all damage river banks. ence of carp (Fletcher et al. 1985; King et al. 1997). In flowing waters, increased turbidity associated with carp density can persist for

Managing the Impacts of Carp 81 CARP

Feeding behaviour Excretion

Zooplankton

Nutrients

Macrophytes Turbidity

Macroinvertebrates Phytoplankton blooms

Other native fauna

direct impacts indirect impacts

Figur e 12: Model of the major effects of carp on structural and process components of the aquatic environment (adapted from King 1995). large distances downstream. The magnitude hectare) had a significantly lower turbidity of effects can also in many instances be site (mean value 47 NTU) than other sites. specific (Fletcher et al. 1985; King et al. Robertson et al. (1997) and King et al. (1997) 1997). adjusted carp in billabongs to be at densities Lougheed et al. (1998) used carp of different of 1180, 1000, 715 and 310 kilograms per densities in enclosures in a marsh in Canada hectare. Carp were found to have a signifi- to show that turbidity, total phosphorus and cant effect on the rates of sediment resus- total ammonia concentrations all increased pension. Carp accounted for 60% of overall as predicted with increases in carp biomass. variance in turbidity in a silty billabong, and in the treatment with the highest biomass of Roberts et al. (1995) found that experimental carp, they were by far the major factor influ- ponds in western New South Wales, when encing turbidity. stocked with carp at densities of 510 and 226 kilograms per hectare, showed an increase in turbidity from 7 to 73 Nephelometric ‘Turbidity, total phosphorus and Turbidity Units (NTU) respectively, over total ammonia concentrations only four days. Malcolm (1971), working in increased with increases in carp Gippsland in Victoria, found a general trend biomass.’ indicating an increase in turbidity in farm dams with the presence of carp. The removal Increased turbidity reduces light penetration, of carp was followed by a reduction in tur- which can lead to lower photosynthetic pro- bidity. duction, and may have detrimental effects on Fletcher et al. (1985), in a study of bill- fish which rely on sight to feed. When sedi- abongs, found the highest turbidity occurred ments settle again, they may smother attach- in a small shallow billabong where carp ment sites for invertebrates and spawning were present at a density of 15–20 kilograms sites for fish. per hectare. In contrast, the billabong with Turbidity can be caused by many forms of the highest carp density (690 kilograms per environmental degradation, particularly of

82 Bureau of Rural Sciences riparian zones and catchments. Many numbers as both events occurred over similar Australian inland lakes and river systems are time periods. There has been no research naturally turbid because of their extensive conducted in Australia to test this hypothesis. floodplains and the types of clay present. On a floodplain, a turbidity reading of less than 5.3.4 Impacts on native fish 17.5 NTU would be considered low (Ladson and White 1999). In a two-year study of the The role of carp in the decline of Australian Broken River, Fletcher et al. (1985) found native fish populations has been the subject turbidity increased downstream from 23 to of much speculation, but scientific evidence 46 NTU, correlating with increased carp is lacking (Harris 1994). There has been con- catches. A maximum value of 75 NTU sideration of declining catch rates of com- occurred when water levels rose because mercial native fish species such as Murray sediments were washed in from the catch- cod (Maccullochella peelii peelii) and golden ment. In Australia storm events deliver the perch (Macquaria ambigua) over the same major sediment loads to Australian streams period as increases in catch rates of carp, but (Cosser 1989; Donnelly et al. 1997), with this correlation does not include a causal link increased inputs downstream associated as many other factors were operating on with land clearing and erosion. During low these native fish species at the time (Section flows clay particles may flocculate and settle 2.1.4). Examination of the declining com- to the bottom. It is in these still waters that mercial catches of silver perch (Bidyanus carp may act as an agent for resuspending bidyanus) and freshwater catfish (Tandanus sediments but carp are not the original cause tandanus) in New South Wales by Reid et al. of the sediments being present. A difficulty (1997) and Clunie and Koehn (1998) found with most studies of carp-induced turbidity is that major declines in both native species that turbidity caused by other fish species is had occurred well before any increases in ignored, so that effects caused by carp alone the catch of carp. Similarly, declines in catch- tend to be overestimated. es of both Murray cod and golden perch occurred during the 1950s, well before the Robertson et al. (1995) also found that carp expansion of carp populations (Derwent had a negative impact on the development 1994; Reid et al. 1997). The diet of carp of epiphytic algae, probably because of includes macroinvertebrates (Section 3.5.1), decreased light penetration caused by carp which may lead to competition with many increasing turbidity. Robertson et al. (1995) native species, but few native fish species found that concentrations of total phospho- (with the exception of freshwater catfish) rus were usually greater with higher carp feed on the benthos in the same way as carp. densities, but there was no consistent patterns for dissolved phosphorus. High carp Whilst there may be some competition densities were also associated with more fre- between carp and native fish for both food quent and intense phytoplankton blooms. and space, dietary overlaps appear minimal Concentrations of chlorophyll a (algae) in and the effects of habitat interactions have the water column were greatest where carp not been quantified. There is little evidence numbers were highest. that carp eat native fish (Section 3.5.1). Benthic feeding carp could, however, ingest Carp have also been reported in overseas demersal eggs of some species. For example, studies to increase phytoplankton concentra- considerable concern has been expressed tions, with an increase in nutrients from over the potential effects of carp on the excretion suggested as the most likely mecha- behaviour of freshwater catfish spawning, nism (Lamarra 1975). One review has sug- guarding nests and the survival of eggs gested that this mechanism may be partly deposited in the nests (S. Rowland, NSW responsible for the intensity of algal blooms Fisheries, pers. comm. 1998), but such inter- in some Australian rivers (Gehrke and Harris actions have not been tested. This concern is 1994). There is certainly a public perception not evident in the Hawkesbury River where of a causal link between increases in these two species coexist (Gehrke and Harris cyanobacterial blooms and increases in carp 1996).

Managing the Impacts of Carp 83 Koehn and Nicol (1998) found overlap in reliance on carp as a food source has not habitat use by native species and carp, with been investigated. both using snags and areas of slower flowing As the causal links for the decline of native fish water. Another pressure on habitat use for populations and fisheries are not fully under- native species may be behavioural pressure stood, it is difficult to forecast the degree of exerted by large schools of large carp, which benefit to native fish populations if carp num- may force smaller native fish from their pre- bers were to be reduced. If carp really are a ferred habitat areas. The high biomass of symptom of river degradation rather than a carp reported for many areas (Section 3.5.4) cause, other measures will also be needed to may have the effect of physical exclusion allow recovery of native fish populations. from habitats for native species.

‘Declines in catches of both 5.3.5 Impacts on native plants Murray cod and golden perch Carp have a major effect on aquatic ecosys- occurred during the 1950s well tems by reducing the density and biomass of before the expansion of carp macrophytes through both direct grazing and populations.’ by physically uprooting plants when feeding (Winfield and Townsend 1991). Several experimental studies have been conducted Benthivorous feeding and destruction of overseas which have quantified such effects: aquatic vegetation by carp may reduce the suitability of habitat for native fish species. • King and Hunt (1967) reported increases Wager and Jackson (1993) suggested carp as of 30% and 75% in the dry biomass of one cause of the decline of several threatened plants in the first and second years of species including: dwarf galaxias (Galaxiella excluding carp with quadrat cages in a pusilla), trout cod (Maccullochella macquar- lake marsh in Michigan, United States of iensis), Yarra pygmy perch (Nannoperca America. An increase in the diversity of obscura) and variegated pygmy perch plant species was also recorded. When (Nannoperca variegata). they completely removed carp from the Gehrke et al. (1996) found recruitment of marsh by poisoning, a 30-fold increase golden perch and bony herring (Nematalosa in the biomass of the attached algae erebi) declined in rivers where carp recruit- (Chara sp.) was recorded over an eight ment was high, but these authors attributed week period. the trends to flow modifications rather than to a direct effect of carp. It has also been sug- • In France, Crivelli (1983) found that gested that carp act as an energy trap, limit- when carp were enclosed in cages at ing the amount of energy available to preda- densities of 450 kilograms per hectare, tors higher up in the food chain (Gehrke 68% of the aquatic vegetation persisted. 1997a; Section 3.5.4). He proposed that carp had not affected vegetation in natural European habitats ‘Benthivorous feeding and where carp densities were less than 59 destruction of aquatic vegetation kilograms per hectare. by carp may reduce the suitability of habitat for native fish species.’ • Winkel and Muelemans (1985) conducted an experimental study in the Netherlands and reported dense mats of Carp are also prey for many native species the attached algae (Chara sp.) appear- including Murray cod, golden perch, trout ing after three weeks of the exclusion of cod, (Section 3.5.2) water rats (Hydromys carp in exclosure experiments. This veg- chrysogaster), and birds such as pelicans etation disappeared again when the (Pelicanus conspicillatus) (Kailola et al. cages were removed. Other plant 1993). Although populations of these species species also recovered when carp were may benefit from the abundance of carp, their excluded.

84 Bureau of Rural Sciences • Meijer et al. (1990) also reported • Bales (1994) and Bowmer et al. (1994) increased abundance of the attached conducted a preliminary experiment in algae (Chara sp.) after two months of equal halves of an irrigation drain in the carp removal in half of two lakes. After a Riverina, New South Wales. They further 16 months, the lake vegetation observed new growth of macrophytes was dominated by a soft-stemmed after the removal of carp from a section pondweed (Potamogeton pectinatus) of irrigation drain. The interpretation of and the density of a filamentous algae this study was complicated by the pres- (Spirogyra sp.) had also increased. ence of carp prior to the experiment.

• Richardson et al. (1990) used 18 large • Roberts and Sainty (1997a, 1997b) experimental ponds with manipulations recorded an oral history of the Lachlan of presence and absence of carp to show River provided by local residents. Many that carp caused a decrease in the amount local residents reported the loss of of algae. It is unclear whether this was aquatic vegetation during the time caused by direct feeding or by an indirect which coincided with the occurrence of effect caused by increased turbidity. carp. Causal links, however, could not be proven. • Lougheed et al. (1998) linked reductions in numbers of plant species to increases • J. Swirepik (NSW Environment in water turbidity in enclosures stocked Protection Agency, pers. comm. 1998) with different densities of carp in a conducted experiments by adding carp marsh in Canada. to large-scale ponds in the Riverina of • Lundhom and Simser (1999) reported New South Wales and recorded poor large increases in submerged macro- macrophyte regrowth in ponds with phyte population densities in Lake carp compared to dense regrowth in Ontario, Canada, when carp densities ponds where carp had been excluded. were reduced from 700 kilograms per hectare in 1996 to 50 kilograms per Although all types of macrophytes have not hectare in 1997. been studied, these studies indicate that shallow-rooted, soft-leaved and submerged vege- Studies on the effects of carp on Australian tation (including attached algae Chara sp.) aquatic plants include: are the growth forms most likely to be affected by carp. • Fletcher et al. (1985) concluded from field studies with carp added to bill- ‘These studies indicate that abongs in northern Victoria, that carp shallow-rooted, soft-leaved and were generally not responsible for submerged vegetation are most destruction of macrophyte beds. They likely to be affected by carp.’ did find a decrease in the abundance of some macrophytes in billabongs follow- It is difficult to study the temporal dynamics ing an increase in carp numbers and of aquatic ecosystems because of the long suggested that high densities of carp time scales over which they change naturally. could eliminate susceptible plant species For this reason, it can be difficult to under- such as pondweed (Potomogeton spp.). stand and predict the responses of rivers to threats and disturbances like carp. Roberts • Roberts et al. (1995) added carp to small and Ebner (1997, Figure 13) provide a simple ponds in the Riverina in New South model which illustrates potential relation- Wales and showed that carp at a biomass ships between carp density, impact and dura- of 226 kilograms per hectare significantly tion of impact, in order to show the problems reduced the number of ribbonweed of using experiments and experimental time (Vallisneria sp.) plants. frames to reveal real impacts.

Managing the Impacts of Carp 85 • Richardson et al. (1990) recorded reduc- t = short tions in chironomids, coleopterans, tri- High (days) chopterans, hemipterans and gastropods in experimental ponds following the introduction of carp.

• Wilcox and Hornbach (1991) recorded t = medium changes in community diversity, rich- (weeks) ness and evenness, but not total densities of invertebrates, at different densi-

Plant abundance ties of carp in cages in the backwaters of a lake in the Mississippi catchment, t = long United States of America. (years) t = medium (months) Zero • Tatrai et al. (1994) used experimental Carp density ponds stocked with different densities of bream (Abramis brama) and carp, finding a decrease in total biomass of ben- Figur e 13: Effect of exposure time on the relationship between carp density and plant biomass remaining. A thos with increasing abundances of hypothetical series of plots, showing the cumulative carp. This was presumably because of effect of carp on four time scales (t), ranging from days predation by carp, and a change in com- to years of exposure. Field impact experiments are munity structure to species with rapid typically of medium length. For a specific carp density life cycles such as oligochaetes and chi- (indicated by arrow on x-axis), there is a huge variation in observed impact, changing from insignificant (high ronomids. plant abundance) to catastrophic (zero plant abundance), depending on the exposure time (Roberts • Lougheed et al. (1998) reported that and Ebner 1997). carp of different densities in enclosures did not have a direct effect on the zoo- 5.3.6 Impacts on macr oinvertebrate plankton community structure, but communities increased turbidities and nutrient loads associated with carp activity resulted in Although the diet of carp consists mainly of a reduced total zooplankton biomass. zooplankton and macroinvertebrates (see They then developed a relationship Chapter 3), there are few quantitative studies between species richness and water tur- of the impact of carp on macroinvertebrate bidities for 19 wetlands in the Great communities. Carp have, however, been Lakes Basin with an apparent turbidity implicated as a secondary factor in the threshold of 20 NTU. decline of indigenous gastropods in the Murray River, through changing the food supply (Sheldon and Walker 1993). Australian studies include: Overseas research from lentic habitats, • Hume et al. (1983b) studied carp diets in includes: the field, but not their effect on macroinvertebrate communities, and found they • Guziur and Wielgosz (1975) recorded fed mainly on algae and zooplankton as considerable decreases in the total num- juveniles (less than 150 millimetres in bers and biomass of benthic macroinver- length), on benthic insects and detritus tebrate fauna in a lake following the as young fish (150 to 400 millimetres in introduction of carp at a density of 153 length) and added occasional plant mat- carp per hectare. The greatest decreases ter to these items when they became in benthic fauna were recorded for chi- adults (greater than 400 millimetres in ronomids and gastropods. length).

86 Bureau of Rural Sciences • Robertson et al. (1995) added and native western carp gudgeon (Hypseleotris removed carp to billabongs in the klunzingeri). This tapeworm may cause high Riverina, New South Wales and found mortalities and is known to affect carp but its that the community structure of epifau- effect on native fish is unknown (Dove et al. nal and infaunal macroinvertebrates 1997). were altered significantly by the carp Spring Viraemia of Carp Virus (SVCV) is not biomass. The species richness of the epi- specific to carp (Section 3.4.4). SVCV has fauna was not correlated with carp been isolated from ten fish species from four abundance but epifauna densities different families (Crane and Eaton 1997) decreased at high carp densities. and is also able to infect fruit flies (Bussereau Infaunal densities were not consistently et al. 1975). However, testing of Australian affected, but densities of the macroin- native fish for susceptibility to the virus, con- vertebrate families Leptoceridae and ducted in England, found that river blackfish Ceratopogonidae were greater with (Gadopsis marmoratus), flathead gudgeon higher carp densities, possibly because (Philypnodon grandiceps), golden perch, sil- of increased algal cell detritus following ver perch, Murray cod, southern pygmy phytoplankton blooms. Carp were also perch (Nannoperca australis) and dwarf found to affect benthic macroinverte- galaxias were not sensitive to SVCV (Hume brate densities. et al. 1983a). These results need to be treated with caution because apart from native fish, tests in England also found that goldfish were not sensitive to the virus. Since then, 5.3.7 Diseases goldfish have been found to be susceptible Pathogens associated with carp are reason- (Crane and Eaton 1997), so that the apparent ably well known and include 226 parasites, lack of sensitivity to the virus in native fish fungal diseases such as that caused by cannot be taken for granted. To date, out- Saprolegnia, eight different bacterial dis- breaks of Spring Viraemia of Carp Disease in eases and two viral diseases (Jeney and wild carp have only occurred rarely if at all. Jeney 1995). The presence of a pathogen, however, does not necessarily result in clini- 5.3.8 Conservation values cal disease. Whilst carp have been implicated in the world-wide distribution of parasites Carp have a major impact on the composi- and pathogens (Hoffman and Schubert tion of freshwater fish communities because 1984), only a few outbreaks of disease in they completely dominate both fish numbers freshwater fish in Australia have been and biomass in many areas. This, together attributed to carp (Laurence 1995), with no with the removal of aquatic plants and specific reports of deaths linked to carp- changes to invertebrate fauna and habitats, is borne disease (Roberts and Ebner 1997). It likely to have altered many of the ecological is, however, possible that such impacts may relationships and ecological processes with- pass undetected if they occur. Goldfish ulcer in aquatic communities. The impacts of carp disease (Aeromonas salmonicida) infects on aquatic habitats and the benthos have goldfish (Carassius auratus) as well as roach been described in this chapter (Sections 5.3.3 (Rutilus rutilus), carp and the native silver to 5.3.7) and there are many impacts on the perch (Humphrey and Ashburner 1993). conservation status of several threatened fish Hume et al. (1983a) found a low parasite species (Wager and Jackson 1993). load in carp specimens collected from north- eastern Victoria, including the parasitic cope- 5.3.9 Links with other issues pod Lernaea, as well as several protozoans. The Asian fish tapeworm (Bothriocephalus Carp are successful colonisers and flourish in acheilognathi) has been found in carp, as degraded environments. Poor water quality, well as in other introduced fish species, such high nutrient loads, frequent algal blooms, as gambusia (Gambusia holbrooki), redfin high water turbidity and bank erosion are perch (Perca fluviatilis), goldfish and the caused by a number of factors in addition to carp (Section 2.1.4). Alterations to flow

Managing the Impacts of Carp 87 regimes and lack of drying of wetland areas catch if fishing off-take reduces carp densi- have also caused changes to aquatic envi- ties. Commercial operators can face a range ronments. The establishment of carp popula- of market problems (Table 10). tions has been assisted by a multiplicity of Kriz (1996) reported findings from market degrading processes. In essence, carp are an research that outlined the future of carp for indicator of a wide range of environmental the domestic market (Table 11). If the weak- problems and, especially in high densities, nesses and threats listed in Table 11 can be also contribute to some of them. converted into strengths and opportunities then there is a possibility of economic 5.4 Resour ce value and expansion. The poor public perception of carp is being addressed with tastings of carp commer cial use and carp products (Easton and Elder 1997). Carp are considered a resource in many More work is being undertaken on the cost parts of the world. The potential value of of value-added products and export oppor- commercial exploitation of carp in Australia tunities (K. Bell, K&C Fisheries, Victoria, is unknown. Estimates have been made but pers. comm. 1998). the only data available are from a few limited ventures at selected sites. Expansion has 5.4.1 Curr ent Australian markets been limited by lack of additional markets for Australian carp. These markets may be Human food for either human consumption or use in products such as fish oils, cattle food, pet Human consumption of carp is limited in food, fertilisers and fish ‘leather’. There is Australia. In 1997, approximately 30% of potential to enhance carp products by value carp harvested in Australian were sent to the adding. The value of all carp products is gen- Sydney and Melbourne fresh fish markets erally low at present which means large (Gooley 1997). Carp are sold from these numbers need to be caught to make an oper- markets mainly to European and Asian eth- ation viable. Carp can be difficult to handle, nic groups. The wholesale price paid at fish as their dorsal spines can catch on nets, so markets varies from $0.50 to $1.85 per kilo- capture methods must be labour efficient. gram. Market fish are sold whole but if the carp are also filleted there is greater opportu- ‘It is necessary to determine nity for other products. Some prices are whether commercial harvesting given by Gooley (1997) in Table 12. reduces a pest’s density Commercial fisherman and restauranteur of sufficiently to achieve desired 25 years, Henry Jones, has served carp in his reductions in environmental Yabby City restaurant in Clayton, South damage.’ Australia, for the past four years. This is believed to be the only restaurant in the country which actively promotes carp as a The commercial use of pest animals has fine eating fish. Recipes include crumbed been considered to reduce the density of carp, carp in oregano with olive oil, carp land vertebrates such feral goats, (Parkes et kiev, vinigarettes, rollmops, smoked carp al. 1996) and feral pigs (Choquenot et al. and carp pate. The popularity of carp dishes 1996). It is necessary to determine whether has steadily increased and now accounts for commercial harvesting reduces a pest’s den- more dishes than any other fish species (H. sity sufficiently to achieve desired reductions Jones, Southern Fishermen’s Association, in environmental damage. This has not been South Australia, pers. comm. 1998). Yabby investigated for carp. The problem for com- City also provides fish and advice on the mercial operators has been low return for a preparation of carp dishes to other restau- high workload with low carp prices deter- rants for special occasions such as cere- ring most operators. There is also an expec- monies for overseas guests. Filleting carp tation of an increase in effort for a lowered properly results in large, boneless fillets and

88 Bureau of Rural Sciences Table 10: Problems and potential solutions for carp marketing in Australia.

Market problem Potential solutions Low market price of carp Use only cost-effective harvesting in selected area. Development of value-added products. Increase quality of product. Ensure correct industry and marketing approach to prevent ‘flooding’. Poor domestic market Develop export markets. Increase product knowledge in targeted local markets. Develop new products. Lack of reliability of supply for markets Increase freezer holding capacity. Schedule harvesting.

Competition from imported fish International negotiations regarding the development of new industries and products. Better marketing.

Table 11: SWOT (Strengths, Weaknesses, Opportunities, Threats) analysis of the carp market conducted by Kriz (1996).

Strengths Weaknesses Supply is plentiful at present Future supply is unknown, catch rates are variable and often unknown. Uncertain supply makes marketing difficult. By-products such as skin – Low prices compared to other commercial species Limited export, carp are easy to culture overseas Positively regarded by Asians and Europeans as food Poorly regarded by Australian consumers as food. Taste of carp is masked in other parts of the world. Complex bone structure gives poor fillet yields. Processing is the only alternative. Potential use in feeds and fertilisers Supply is unknown. Market difficulties Useful in value-added products, such as smoked or dried Little is known about processes and costs products for value-added products

Opportunities Threats Niche market for skinless, boneless and branded fillet that Aquaculture carp production is efficient is low priced and widespread in carp-producing countries

Carp as raw material for surimi Imports of carp may increase by establishing a market for the product Processed products for human consumption such as fish Negative public perceptions may persist cakes, fish balls, canning or other processing despite active marketing of carp products

Managing the Impacts of Carp 89 Table 12: Values of carp (after Gooley 1997). Point scale: * good quality off fillet (estimated 15–20% of total catch); ** gilled and gutted; *** gutted; Prices are wholesale (delivered) in dollars per kilogram (unless otherwise stated).

Human consumption Dollars per kilogram Chilled and smoked whole fish** 0.80 Chilled and smoked prime-cut fillets (skinless, boneless) 2.50

Tinned fish 0.32 Fish balls, cakes and mince no figures available

Cured (smoked or marinated) small goods no figures available Dried whole fish and sprinkle type seasoning no figures available Surimi 2.50 Fish protein concentrate*** 0.11 Non-human consumption Fish meal 0.15 Fish oil 0.11 Liquid fertiliser 0.15-0.20 Stock and fish food ingredient (wet or frozen biomass) 0.03 Tanned fish skins 0.50 per skin* Crayfish bait 0.30-0.50 Processed recreational fishing bait 0.15 Pet food ingredient (wet or frozen biomass; replacement for no figures available mackerel and pilchards

Despite having a complex bone structure, proper filleting of carp can produce large fillets and boneless strips suitable for a wide range of fish dishes. Source: A. High standards of post-harvest handling are critical to Brumley, East Gippsland Institute of TAFE. maximise the commercial value of carp. Source: A. Toovey, NSW Fisheries.

90 Bureau of Rural Sciences boneless strips suitable for a large range of pers. comm. 1998). Carp from the Gippsland fish dishes. Yabby City is operated in con- Lakes often come from brackish water, junction with a commercial operation, fish- which may enhance their eating qualities, ing for both native fish and carp in the lower although this has not been tested. Murray River, and sells carp directly as a table fish or a range of other products. Fresh Crayfish and rock lobster bait boneless carp fillets are sold for $6.50 per kilogram whilst smoked carp can fetch up to About 40% of Australian carp harvested are $10 per kilogram. Retail prices for whole sold for bait to the rock lobster industry carp are up to $7 per kilogram in some (Gooley 1997). Small carp are frozen into Sydney shops. blocks and transported to the fishing ports of south-eastern Australia. The peak of demand Carp for the domestic market come mostly coincides with the summer catches for rock from two lake areas in Australia: the Coorong lobster and is zero during the winter off-sea- and Lake Alexandrina area in the lower son. Prices for this market range from $0.30 Murray River in South Australia and the to $0.50 per kilogram (K. Bell, K&C Gippsland Lakes in Victoria. In South Fisheries, Victoria, pers. comm. 1998). Australia, some 30 licensed commercial operators target a range of native and introduced In South Australia, the availability of carp as species, mainly with mesh nets. The carp crayfish bait has been variable. Larger stor- from Lake Alexandrina are transported to age freezer facilities are needed to ensure a Adelaide and then to the Sydney market (H. more constant supply (H. Jones, Southern Jones, Southern Fishermen’s Association, Fisherman’s Association, South Australia, South Australia, pers. comm. 1998). In pers. comm. 1998). Even carp used for cray Victoria, the 18 operators in the Gippsland bait need to be fresh because mucus pro- Lakes mainly use mesh nets and large seine motes bacterial growth which makes the bait nets to target native fish, especially black less attractive. It is a misconception that bream (Acanthopagrus butcheri). If carp are waste carp can be marketed for cray bait and caught in small numbers they can be sent for other products (K. Bell, K&C Fisheries, domestic use. Smaller quantities of carp are Victoria, pers. comm. 1998). caught commercially from rivers and lakes in New South Wales. Fertiliser In the Gippsland Lakes, commercial opera- The amount of carp used in the production tors selling carp to wholesale markets of liquid fertiliser is currently low but is between 1993 and 1998 obtained prices of increasing. One product, ‘Charlie Carp’ tar- $0.20–$1.50 per kilogram (D. Allit, gets the domestic nursery and home garden Gippsland Lakes Fisherman, Victoria, pers. market. Made from pulped carp and rice comm. 1998). Generally the prices are fibre, the liquid fertiliser is sold for home gar- extremely low, less than $1 per kilogram, deners in one litre retail bottles or 20 litre compared to the native black bream which containers for farm use. As the price paid to fetches $8–$10 per kilogram. Commercial the commercial harvester for this product is exploitation is not possible by operators as low as $0.15 per kilogram (Table 12), who only catch carp as a non-target species. large quantities of fish must be readily avail- Carp dominate the catch from the Gippsland able for harvesting to be economically Lakes area. In 1995, the commercial catch of viable. Fish needs to be fresh to ensure the carp was 334 tonnes of the total 653 tonnes fertiliser is of a satisfactory quality. of fish. One operator (K&C Fisheries, Section 5.4.3), solely targets carp and supplies mar- Cattle feed kets in Melbourne and Sydney. Quality fish, handled appropriately, fetch higher prices. A report of an enterprise manufacturing cat- Carp are placed in ice slurry to preserve flesh tle feed from carp made in 1997 (Water quality and flavour and to prevent bacterial Rabbits documentary 1997) indicated the growth (K. Bell, K&C Fisheries, Victoria, average price paid was $0.10 to $0.35 per

Managing the Impacts of Carp 91 kilogram of carp (Wilson 1998), which Value of Australian exports showed a need for large quantities of carp at low prices. Fish of all sizes could be used for A marketing study conducted by Kriz (1996) this product, but again they must be fresh. concluded that the export of carp from Australia for human consumption was not 5.4.2 World markets and world viable because they are cultured easily in many other countries. The production of carp pr oduction in countries where carp are desirable must be Carp are easy to produce and are a good high to meet the demand. Cultured carp in source of protein with the main production of these countries are being used to restock nat- carp for human consumption occurring in ural waters for recreational catches. China (Lin and Peter 1991). Chinese carp pro- In Poland, the 1990 production of carp was duction from aquaculture was estimated to be 20 000 tonnes (Kriz 1996). In 1997, a Polish 3 275 000 tonnes in 1990 (Kriz 1996). The dom- importer recognised it was economically inance of carp production in China is over- viable to import Australian carp (Keith Bell, whelming, although India, Bangladesh and K&C Fisheries, Victoria, pers. comm. 1998). In Indonesia also produce carp through pond January 1998, a contract was signed with K&C aquaculture. Even though these countries pro- fisheries to export a minimum of 300 tonnes duce less carp than China, production in India to Poland over the following 12 months. is still approximately twice that of individual These carp come from the clean waters of the European countries. In Japan, there is strong Gippsland Lakes where they are collected consumer demand for marine fish products, so with high standards of handling and ice carp are not produced for food as much as in preservation. The carp, of up to six kilograms other Asian countries. The Koi strain of carp in weight, are headed, gutted and tailed, then features in Japan as an ornamental fish. exported frozen. The process follows strict Aquaculture is also a large industry in most license requirements from the Australian European countries today. Total production of Quarantine and Inspection Service (AQIS). carp in 1990 ranged from 7000 tonnes in Bulgaria to 392 806 tonnes per annum in the ‘The fact that Australian carp USSR (Kriz 1996). Research on carp includes are grown in rivers and not aquaculture with other species (polyculture), farmed is seen as an advantage conservation of the gene pool and productivity for the German market.’ of ponds and natural ecosystems. In the Czech Republic, the Research Institute of Fish Culture and Hybrobiology aims to improve the culture An Australian company, Australian Abalone of common carp (Z. Adamek, University of Exports Pty Ltd, has established companies Southern Bohemia, Czech Republic, pers. in Germany, Israel and Spain to export a comm. 1997). Carp are frequently stocked into range of value-added carp products. The eutrophic reservoirs of central and eastern German company, called Australian Europe to enhance fish production (Bninska Gourmet Imports, uses the brand name River 1991). In 1990, trout accounted for 81% of Gold and a marketing spiel of ‘Cyprinus car- aquaculture fish production in Europe with pio, simply the best’. The range of carp prod- carp constituting 13% (Kriz 1996). The low ucts includes canned, smoked and dried production of carp in aquaculture in Europe carp, carp jerky, a soup additive, carp au may be partly attributable to the dominance of naturel, carp in abalone sauce, carp in cyprinids in the wild fishery. The production piquant sauce and a product developed in of wild salmonids (Salmonidae) has dimin- accordance with Jewish kosher require- ished in Europe compared to the cyprinids. ments. The fact that Australian carp are Wild fishing for carp still occurs in Europe in grown in rivers and not farmed under aqua- the Caspian and Black Seas and eastern culture conditions is seen as an advantage Europe (Bninska 1991, Z. Adamek, University for this market (F. Glasbrenner, Managing of Southern Bohemia, Czech Republic, pers. Director, Australian Abalone Exports Pty Ltd, comm. 1998). Victoria, pers. comm. 1999).

92 Bureau of Rural Sciences 5.4.3 Curr ent Australian pr oduction It appears that there are sufficient wild stocks of carp available in Australia to satisfy The standing stock of carp in Australia is not an expansion of existing markets. known, but is thought to be in the order of tens of thousands of tonnes (Gooley 1997). Professional commercial fishing operations An assessment of the carp stock in New based solely on carp have occurred in South South Wales of 76 000 tonnes was produced Australia and Victoria along the Murray by Wilson (1998) using carp population and River. In Victoria, carp have been harvested distribution estimates from Harris and from the Gippsland Lakes for the past 14 Gehrke (1997). Wilson’s estimate includes years. The Gippsland Lakes carp fishery was carp in dams and water storages not included worth $375 000 in 1996–97 with a total catch in the population survey and is likely to be of 478 tonnes. This represented 85% of the far higher than any estimate of potential har- total carp catch in Victoria, a proportion that vest because much of the resource is in has been consistent over ten years (Figure remote areas where full exploitation would 14; Keith Bell, K&C Fisheries, Victoria, pers. be difficult. Carp fisheries have not been sub- comm. 1998). The catch of carp reflects the jected to stock assessments in Australia. Carp market demand but not necessarily constant production levels reflect demand: where carp numbers. The black bream catch in the profitable markets exist, production occurs Gippsland lakes (Figure 14) has declined (Table 10). Gooley (1997) gave an estimate of during the same time (Coutin et al. 1997). 5000 tonnes of carp per annum to be the Markets for carp are discussed in a case accessible and biologically sustainable yield study of the main commercial operation in across south-eastern Australia. Victoria (Box 1) (K. Bell, K&C Fisheries, Total Australian carp production in the 1990s Victoria, pers. comm. 1998). Important fea- has ranged from 900 to 1675 tonnes per tures of this successful carp harvesting opera- annum with the approximate breakdown by tion are: State as follows: • large numbers of carp are caught • Victoria, 300–600 tonnes per annum efficiently • South Australia, 500–1000 tonnes per • methods are available to handle the huge annum weight of fish • New South Wales, 100–175 tonnes per • methods are available to avoid the carp’s annum. spines

Figur e 14: Catches of carp and black bream in Gippsland Lakes, Victoria, from 1987–88 to 1997–98 (Department of Natural Resources and Environment, Victoria 1998). Reproduced with the permission of Department of Natural Resources and Environment, Victoria.

Managing the Impacts of Carp 93 • fresh fish are sent to market in constant low amounts A B • handling methods ensure quality is maintained for carp for all markets

• some carcasses are put to multiple use C

for a range of products damage Total

• storage and freezing facilities are available for non-peak times for some markets

0 • research is conducted into new markets and value adding Carp density

• efficient transport is available to capital Figur e 15: Possible relationships between carp density cities. and the damage they cause. For example, line A might represent the damage carp cause to an aquatic plant that carp disturb even when they are at low densities. Line B Further details of carp harvesting and mar- could represent direct competition between carp and keting operations are given in the damage native fish for a limiting resource. Line C could occur if control case study (Box 2; Section 5.4.4). there is little or no competition between carp and native species for habitat when carp are at low densities. The shape of these lines will depend on the type of resource 5.4.4 Commer cial harvest as being affected and other variables such as interactions damage contr ol between species and seasonal conditions. If ongoing commercial harvesting is to be a viable control method, it must reduce and sustain carp densities at levels where damage is reduced to acceptable levels. Determining these levels requires better knowledge of carp density–damage relationships (Figure 15, see also Appendix A, Step 3) so that a target carp density can be set to meet resource protection goals (Bomford and Tilzey 1997; Choquenot and Parkes, in press). If the carp density required to achieve damage control goals is relatively low (Figure 15, line A), it is likely to be Cost of removing more carp uneconomic for commercial harvesting in most areas unless the profitability of the industry, particularly the product value, increases dramatically. This is because, as Carp density carp density declines, the cost of harvesting additional fish increases steeply (Figure 16, Figur e 16: Relationship between carp density and cost Bomford and Tilzey 1997). If, on the other of removal using conventional commercial harvesting hand, carp only cause unacceptable techniques. damage when their density is high (Figure 15, lines B and C), then commercial harvest- Bomford and Tilzey 1997). Fortunately it is ing to meet resource damage control objec- likely that, for most forms of environmental tives may be economic, because harvesting damage, at the low densities when costs of would not be required at the low densities removal are high (Figure 16), damage levels where the cost of removal is high (Figure 16, are also usually low (Figure 15, lines B and C).

94 Bureau of Rural Sciences To estimate the stock of a fish, recruitment to fish with labour efficient gear such as rates need to be known. These are not large seine nets. Remote locations add costs known for carp (Thresher 1997) and only for refrigeration, handling and transport. predictions based on populations that follow Commercial harvesting would not solve the density-dependent limitations have been problem of future recolonisation by carp. used. It is likely that carp populations are The question of how to reduce carp numbers also vulnerable to environmental variations in strategic places and continue to maintain (Section 3.4.3). Spawning and successful viable markets needs to be addressed. The recruitment may be linked to floods and two goals may be mutually incompatible and there are also periods of slow growth theoretically commercial use should have no (Section 3.4.3), so that predicting a carp ongoing value for damage control. It would stock in any one year may be difficult. be counter-productive if the need to protect Roberts and Tilzey (1997) gave a high priori- investments and maintain markets leads to ty to the need to understand carp population harvesters objecting to carp control strategies dynamics. Population parameters for differ- being implemented. The demand by con- ent areas and habitats are needed to assess sumers also needs to meet the level of pro- the effects of carp harvesting as a control duction which will coincide with the desired measure. In some areas, a one-off harvesting level of carp abundance. Commercial har- operation may be allowed with an under- vesting could possibly manage and minimise standing that fishing may not continue. carp impacts in some areas if these levels coincided. The establishment of a carp har- ‘Commercial operations may vesting industry based on ongoing and sus- need to be supplemented by tainable catches however, is only likely to additional carp removal to keep hinder the control of this species in the long densities below damage control term. thresholds.’ The role of commercial harvesting as a population control is discussed in Sections 7.3 and Whilst commercial harvesting is not feasible Box 1. It will be necessary to monitor carp on a widespread basis (Section 7.3), it may stocks to identify changes in age and size be used as a form of carp management to structure, reproduction and longevity and reduce damage caused by carp in some mortality resulting from control efforts restricted areas. At low densities, commercial (Section 10.2.2). carp harvesting is not profitable and so will Key aspects regarding the future of carp use often fail to reduce carp densities enough to were identified by Gooley (1997). The fol- meet damage control goals. In such cases lowing features would need to be integrated commercial operations may need to be sup- into a plan if commercial carp use was added plemented by additional carp removal to to damage control goals: attain and keep densities at (or below) damage control thresholds. • carp use requires value-adding Commercial harvesting for carp is restricted • Quality Assurance Programs are integral in many areas by both legal and logistic rea- to value-adding sons. Only about 5% of rivers in New South • cost-benefit varies with markets and har- Wales were accessible to commercial fishers until 1999, when area restrictions were lifted vesting costs for carp harvesting. About 30% of the Murray • carp production is a business. River in South Australia is currently open to commercial fishing. Commercial fishing is even more restricted in Queensland and lim- To date most commercial harvesting has ited to restricted waters in Victoria. Many of occurred in limited areas where high num- the waters which contain carp have limited bers of carp are readily available. Given the access and are difficult to fish. Large snaggy low current price for carp, opportunities to rivers and billabongs are especially difficult expand harvesting into new areas with lower population densities are limited.

Managing the Impacts of Carp 95 Box 1: Case study of lar ge carp harvesting operation: sustained contr ol

K&C Fisheries, based in Sale, Victoria, has been run by Keith and Cate Bell since 1984, refining methods for targeting carp. Keith uses a 732 metre seine net (Figure 18) in Lake Wellington, where much of the lake is relatively shallow and has few snags, allowing the hauling of a seine. For most of the year, he hauls in about 18 tonnes of carp a week. The efficiency is increased with the use of a large storage boat which can be trailered to his premis- es. K&C Fisheries carp processing factory. Source: A. Brumley, East Gippsland Institute of TAFE.

The carp are held in ice slurry in the vessel and transported to the processing plant where the ambient temperature is 5°C. A special room to head, scale and gut the fish for export has AQIS approval. The company provides a wide range of high quality carp products including fresh table fish for the Melbourne and Sydney markets, prime cut fillets for seasoning and various smoked and dried carp speciality Electrofishing is one of the carp harvesting techniques employed by K&C Fisheries. Source: Lisa Crisp, East lines. Non-human uses which provide Gippsland Catchment Management Authority. markets include rock lobster bait and fertiliser. Having researched the potential for exporting carp into Asia and Europe they A boat with electrofishing equipment has now supply carp to Poland for human con- been specially designed for harvesting sumption. In 1998, 300 tonnes were carp in the lakes and its tributaries so that exported. Such exports could significantly carp can been exploited when they occur expand production with a target of 1000 in large numbers. As the salinity of the tonnes set for 2000. lakes system fluctuates, carp move out of brackish into fresher areas where elec- Even before the stringent requirements for trofishing is possible. Up to three tonnes of an export licence with AQIS were met, the fish can be removed in one day using an business was established with the Quality operational boat and a small boat which Assurance Program consistent with can hold nearly one tonne of fish. Australian seafood industry standards. High quality handling and use of ice have There has been extensive ongoing capital ensured the high value of their products. investment in special equipment, includ- Packaging and domestic freight services ing a seven tonne capacity fishing vessel, are specialised to ensure maximum quality large-scale, purpose-built nets, a large control over their products. Keith Bell blast tunnel freezer to snap freeze large believes that the quality of carp meat has a quantities and a large capacity storage lot to do with post-harvest handling, some- freezer. In 1999, K&C Fisheries produced times more so than the quality of the water more than 900 tonnes of carp for the from which the carp are sourced. export and Australian domestic market.

96 Bureau of Rural Sciences Box 2: Commer cial harvest as one-of f damage contr ol in Sewerage Ponds, Linder now, East Gippsland W ater . (J. Kostarakis, Technical Manager, East becoming suspended in the treated efflu- Gippsland Water, Victoria, pers. comm. ent, so it was decided to remove carp from 1999) the lagoons. A contractor, K&C Fisheries from Sale, was Site engaged to net the carp using a seine net. East Gippsland Water has responsibility for A total of 53 carp, up to 10 kilograms in water and waste water services in many weight, were removed from the lagoons. towns throughout the East Gippsland area. The operation cost $1000. The contractor One of these towns is Lindenow, where removed the carp from the site and they the Authority manages a waste water sys- were used for making fertiliser. tem with some 125 connections. Evaluation Problem • The low operational cost was possible because the carp were sold for Waste water is pumped from the town to making fertiliser. treatment works consisting of three lagoons which hold 11 megalitres of efflu- • In the four months preceding removal ent and waste water. Effluent from these lagoons is discharged to a confined wet- of carp, two of the four monthly land. An Environment Protection Authority samples failed the licence limits for licence, which sets parameters for the suspended solids. In the six months quality of effluent discharged to the wet- following the removal of carp, all six land, covers operation of the whole sys- monthly samples passed the licence tem. limits for suspended solids.

Occasionally, testing the effluent has • The time it will take for carp detected failure to meet licence require- populations in the lagoons to recover ments for suspended solids. will determine the cost-efficiency of the operation. If carp increase and One-off control cause future problems, another con- It was suspected that these failures may be trol operation will be needed. due to the presence of carp in the lagoons which stir up sediments, with fine particles

Managing the Impacts of Carp 97

6. Past and curr ent management

Summary Following community meetings and public discussions on the problem of carp during In the past there has been no coordinated the early 1990s and the ‘national carp sum- management of carp in Australia and carp mits’ in 1994 and 1995, public interest and control has been mainly undertaken by media attention to carp has grown enor- State and Territory agencies, predominantly mously. This public attention and pressure fisheries agencies. Carp are declared nox- has prompted government agencies to ious (or equivalent) in Queensland, acknowledge carp as a possible pest species Victoria, Tasmania, and South Australia, and to examine options to address perceived with supporting regulations and penalties problems caused by carp. The resurgence of for possession. Management has been mini- interest in recent times is similar to the inter- mal in most cases, except for some new est exhibited in the late 1970s following the invasions where eradication has been rapid spread of carp through many river sys- attempted. Other management approaches tems. include encouraging commercial harvesting and recreational fishing to remove fish. ‘Public attention and pressure In recent years the formation of the has prompted government National Carp Task Force, as a result of public interest and pressure, has promoted a agencies to address perceived more coordinated approach and national problems caused by carp.’ focus on carp control. A Carp Control Coordinating Group has also recently been formed with State, Territory and Federal 6.2 National management government representatives to coordinate carp control on a national basis. The need for a national approach to carp management has only emerged recently and 6.1 Public pr essur e for action is still being developed and refined. Until recently, management of carp has not been Following the publicity accompanying the coordinated on a national or even a regional rapid expansion of carp (Cyprinus carpio) in scale. Generally carp management has been Australia during the 1970s and early 1980s, restricted to sporadic attempts to eradicate public interest waned until the 1990s. The new invasions and opportunistic commercial Victorian Carp Project conducted from 1979 to exploitation. The management of carp has 1982 found little direct evidence linking carp been perceived by many as the responsibility to environmental degradation. Those results of State and Territory agencies, mainly fish- led government agencies to adopt policies eries departments (Table 13). which treated carp as a nuisance that had to be Importation of live carp is restricted because lived with and could be commercially exploit- carp are not listed on Schedule 6 under the ed in some circumstances (Hume et al. 1983a; Wildlife Protection Act 1982 which contains Reynolds 1987), rather than as a species that a list of species approved for import by caused widespread environmental damage Environment Australia. Goldfish (Carassius requiring active management. More recently auratus) are listed, although there is current- there has been a growing ground swell of ly a review of ornamental fish import regula- popular opinion, increasing awareness of tions following the detection of Spring environmental damage to river systems from a Viraemia of Carp Virus (Rhabdovirus carpio) variety of causes, and scientific evidence of in goldfish in Hong Kong. Spring Viraemia of damage caused by carp, which has led to an Carp disease has the potential to affect carp increase in public and government activities in populations (see Chapter 7) should the dis- relation to carp management. ease enter Australia. Import risk analyses

Managing the Impacts of Carp 99 of Fisheries WA Not declared a pest non-translocation law, education, raising of community awareness Enforcement Fisheries Act 1994 , Inland Fisheries Commission education, raising of community awareness Enforcement Fisheries Act 1995 SA Fisheries, South Australian Research and Development Institute Enforcement, education, raising of community awareness Fisheries Act 1982 VIC SA TAS WA Fisheries Victoria, Department of Natural Resources and Environment Enforcement, education, raising of community awareness. Fisheries enforcement officers to check use of live bait and transport

Noxious Exotic Controlled fish Fisheries Act 1995 ACT Environment ACT Not declared a pest Education, raising of community awareness Fisheries Act 1967 cy NSW

Not declared noxious, but recognised as a pest by poli Enforcement, education, raising of community awareness, inter-agency cooperation Fisheries Management Act 1994 QLD Noxious DPI for QFMA NSW Fisheries Enforcement, education, raising of community awareness Fisheries Act 1994 Import of live carp prohibited CCCG, MDBC, Environment AFFA, Australia Commonwealth Checks by customs and quarantine officers Wildlife Protection (Regulation of Exports and Imports) Act 1982 Status of carp, responsible managing agencies and relevant legislation for carp management in Australia. Responsible management agencies Status of carp Actions undertaken Relevant legislation Table 13: Table

100 Bureau of Rural Sciences being undertaken may indicate the need for to facilitate the development of a series of health checks of imported goldfish to ensure major field projects which identify and publi- that there is no clinical evidence of disease cise the positive impacts of the removal of (P. Durham, Animal Quarantine Policy carp. Information on current projects has Branch, Australian Quarantine and Inspection been placed on a database. The NCTF pro- Service, ACT, pers. comm. 1998). duces a public newsletter Cyprinus (National Carp Task Force 1996a,1996b) which pro- 6.2.1 National Carp T ask For ce vides information on carp. The National Carp Task Force (NCTF) was Commercial exploitation — The intention of established in January 1996 to consolidate assisting and coordinating the commercial and focus community energy on the growing exploitation of carp has been enhanced by problem of carp. The Task Force was formed the inclusion of two commercial operators following a second National Carp Summit on the NCTF. The NCTF has also made small held by the Murray–Darling Association in amounts of funding available for the devel- Renmark in October 1995. This summit built opment of business plans for groups or indi- on other community meetings about carp viduals who wish to exploit carp for com- which had been held across the mercial use and to individuals or groups who Murray–Darling Basin in 1995 and followed wish to develop concept plans for the reduc- on from the first summit in Wagga Wagga in tion of carp in wetlands. 1994. Legislation — The NCTF aims to collate all The aim of the NCTF is to eradicate carp legislation relating to carp and provide its from all Australian aquatic habitats through a views on areas where legislation could be strategic action plan that promotes coordi- appropriately amended. nated research, provides good information, explores commercial opportunities and 6.2.2 Carp Contr ol Coor dinating seeks complementary legislation. The NCTF Group believes that control will be best achieved through a natural resource management In response to an earlier agreement by the strategy, using pest management principles, Murray–Darling Basin Ministerial Council for rather than relying only on fisheries tech- the Murray–Darling Basin Commission niques. (MDBC) to take a leading role in the coordination of appropriate action for the control The NCTF has membership from of carp, a proposal for the formulation of a Commonwealth and State and Territory agen- Carp Control Coordinating Group (CCCG) cies with an interest in carp, researchers, was developed and discussed with recreational and commercial fishers, local Commonwealth agencies in 1996. In January government and the angling community. The 1997, the Standing Committee on Fisheries Murray–Darling Association currently con- and Aquaculture endorsed this approach in a venes the NCTF and provides secretarial sup- letter from the Ministerial Council on port with funding provided through the Forestry, Fisheries and Aquaculture (MCFFA) Murray–Darling 2001 FishRehab program. and nominated representatives from fish- In 1997, the NCTF developed an action plan eries agencies in the States and Territories which has research, information, commercial and the Commonwealth. At a MDBC Meeting exploitation and legislation objectives as fol- 42 in 1997, Commissioners noted that the lows: coordination role for the Commission was in providing a Secretariat and Chair to the Research — To promote research into the CCCG, and that resourcing this arrangement control methodology of carp. The role of the would rely on funding from the $13 million NCTF is to coordinate and facilitate, not carry contained in the Commonwealth’s Natural out, research work. Heritage Trust for Water, the Environment Information — To facilitate the open and Fish Management (now called the exchange of information regarding carp and Murray–Darling 2001 FishRehab Program).

Managing the Impacts of Carp 101 The objectives of the CCCG are set out in the 6.3 State and T erritory following Terms of Reference: management • review available information to determine the impacts of carp Carp are declared noxious pests in Queensland and Victoria and are considered • develop a national strategic research exotic in Tasmania and South Australia, so in plan for carp control and management all these States it is illegal to keep, release or that establishes research needs and transport carp. Carp are acknowledged as priorities for: pests in New South Wales, and transport and release of live carp is prohibited. The spread – defining the economic and ecological of carp is not considered desirable in any impacts of carp State or Territory and some States have – developing carp control methods attempted eradication programs on a local scale. The responsibilities of the managing • review current management strategies, agencies vary with the status of carp and the prepare an interim national manage- associated legislation (Table 13). Legislation ment strategy and recommend appropri- by itself, however, is not an adequate ate management plans for the long-term response to managing the damage caused by control of carp carp and probably has little effect on carp populations. While it is not the role of the • advise the NCTF on the preparation of managing agencies to remove carp, some material to inform the community on agencies organise fishing competitions carp related issues and/or encourage commercial harvesting. There are no size or bag limits for carp, or • promote effective liaison between waters closed to the taking of carp, in any groups conducting carp research, man- Australian State, but there is an overall bag agement or control limit for fish caught in the Australian Capital Territory (Kailola et al. 1993). New fisheries • report to the relevant Ministerial legislation was tabled in March 2000 which Councils (Murray–Darling Basin will remove the overall bag limit in the ACT Ministerial Council, MCFFA, Agriculture (M. Lintermans, Environment ACT, pers. and Resource Management Council of comm. 2000). Australia and New Zealand, Australia and New Zealand Environment and 6.3.1 Victoria Conservation Council) with a national strategic research plan and an interim The Fisheries and Wildlife Department dis- management strategy. couraged a proposed venture to import carp into Victoria from Germany for the purpose Intended outcomes of the CCCG include: of aquaculture in 1960. However, while the Fisheries Act 1958 prohibited the stocking of • improved awareness and coordination non-indigenous fish, including carp, in pub- of activities relating to the research and lic waters, it did not prohibit this in private management of carp across all relevant waters. By 1961, carp had been imported, Ministerial Council sub-committees and sold and liberated into farm dams in many State and Territory managing agencies parts of Victoria. The then Director of Fisheries visited the United States (State • a national strategic approach to address- Development Committee 1962) to assess the ing the carp issue. potential impacts of carp and by December 1961 their sale had been prohibited. Debate A Memorandum Of Understanding exists about carp led to an inquiry and the declara- between the NCTF and CCCG and each has tion of the Noxious Fish Act 1962 which had membership with the other body. penalties for the possession of carp and allowed Fisheries and Wildlife officers to

102 Bureau of Rural Sciences enter private property and destroy carp. In accidental introduction of live fish into pub- May 1962, a carp-kill program began to lic or private waters within a Victorian river attempt to eradicate carp before they could catchment in which the taxon to which the breed in spring. More than 1300 dams were fish belongs cannot reliably be inferred to poisoned and later tests of 200 of the treated have been present prior to the year 1770 AD’ dams did not find carp and so the eradica- is listed as a Potentially Threatening Process. tion was deemed to be successful. The listing of this process means that a man- Unfortunately, carp had either escaped into agement plan must be produced by the the La Trobe River or had been stocked ille- Department of Natural Resources and gally into other waters and the spread of Environment to outline how it intends to carp continued (Clements 1988; Victorian manage introduced fish species. Fisheries 1991a). Fisheries Victoria is currently active in pro- moting the commercial exploitation of carp. ‘Carp are defined as being pests As part of this they are undertaking an when they occur in biomass assessment of the economic basis and mar- greater than 450 kilograms per kets for the carp industry. Fisheries Victoria hectare.’ has produced issues of their widely distributed Victorian Fish Notes and Infosheets which relate to carp. Victorian Fish Notes number The Victorian Fisheries Policy issued in 1988 14 ‘Carp in Victoria’ (Victorian Fisheries and revised in 1990 and 1991, Statement on 1991a) provides a history of carp in Victoria, Noxious Fish — Carp (Victorian Fisheries early management and some results of 1991b), states that: ‘Because carp Cyprinus research into carp. The Fisheries carpio have the potential to cause ecological Management Infosheet Number 8 ‘Policy and environmental problems, legislation has Statement, Noxious Fish — Carp’ (Victorian been enacted to prevent their spread in Fisheries 1991b) outlines policy, a brief his- Victorian waters. Carp will be treated as both tory and biological facts and potential meth- a resource and an occasional pest. Carp are ods for control of isolated populations. defined as being pests when they occur in Infosheet Number 10 ‘Removal of carp from biomass greater than 450 kilograms per farm dams by poisoning’ (Victorian Fisheries hectare in ecologically, recreationally or eco- 1991c) outlines methods and procedures for nomically valuable water bodies, unless this control method. there are strong arguments for acting at lower biomass densities. Regional staff will Coarse angling for carp (Section 4.9.2) has be responsible for making the biomass esti- also had some limited support in Victoria mates and for reducing the biomass density with special permits being issued by in the approved waters. The Department will Fisheries Victoria for some coarse fishing not remove carp from private waters, except events. These permits are only issued to the in an isolated water body located in a previ- Australian Federation of Coarse Anglers ously carp-free catchment. Carp will remain Association for fishing competitions held in on the noxious fish list. This policy covers all specified waters where carp numbers are varieties of Cyprinus carpio including Koi, high. The permits allow members to release mirror and leather varieties. The Department live carp back into waters after their capture supports commercial harvesting of carp, sub- at competitive fishing events (R. Winstanley, ject to regional supervision.’ Recreational Fisheries, Fisheries Victoria, pers. comm. 1999). Coarse angling was also The Fisheries Act 1995 was amended in 1997 promoted in a front page feature in the June with noxious species being covered under 1998 issue of ‘Fishing Lines’, the newsletter Sections 75, 76 and 81. Proposed Fisheries of the peak angling body in Victoria (VRFish Regulation (1998) 530 (2) states that: ‘a per- 1998). son must not use live carp (including goldfish) as bait in inland waters’. Carp are also included under the Flora and Fauna Guarantee Act 1988 where the ‘deliberate or

Managing the Impacts of Carp 103 6.3.2 New South W ales • identifying fishing gear and methods most suited to large-scale carp removal Carp management has become an increas- ingly important issue in New South Wales as • identifying cost-effective levels of carp knowledge and understanding of carp control relative to the degree of environ- impacts has slowly improved and the com- mental benefit achieved munity have demanded greater action. This change is evident when comparing the poli- • providing guidelines for water man- cy outlined in the original NSW Fisheries agers, community groups and other AgFacts on European Carp by Reynolds organisations on the most efficient and (1987), which suggested that the detrimental cost-effective approach to controlling effects of carp were doubtful, and in the carp populations in enclosed water bod- updated version by Brown (1996), which identified environmental damage caused by ies. carp. Although the Fisheries Management Act 1994 provides for the declaration of noxious fish species, carp have not been listed to Commercial carp fishing date. The Carp Production Incentive Scheme (CPIS) aims to facilitate the development of ‘A Carp Assessment and new and existing markets for carp and carp Reduction Program (CARP) was based products through enhanced commer- implemented in 1998 to run over cial fishing. This is undertaken with a view to three years.’ establishing a self-supporting commercial carp fishery. A $1 million Carp Assessment and Reduction In 1998, four licenses were established for Program (CARP) was implemented in 1998 carp harvesting teams to participate in a limit- to run over three years. This project is man- ed duration subsidy program. Each team aged by NSW Fisheries with the support of a received payments of 25 cents per kilogram steering committee including representatives for carp caught during 1999, up to a maxi- of the NSW Department of Land and Water mum of 250 tonnes. This was designed to Conservation, NSW Agriculture, NSW offset the cost of developing fishing meth- National Parks and Wildlife Service, and the ods, transport systems, processing tech- NSW Department of State and Regional niques and markets for carp. Payments will Development. be reduced to 15 cents per kilogram in 2000 and 10 cents per kilogram in 2001. Carp har- The CARP program aims to reduce carp pop- vesting teams have access to a wider range ulations and impacts in New South Wales, of fishing methods and geographical areas through: than other fishers in order to maximise carp • developing a commercial carp fishery production. However, at the time of publication, only three licenses have been issued. • developing a recreational carp fishery The CPIS has a number of important differences from conventional bounty schemes. • educating the community about carp Firstly, its main objective is to support the impacts and control methods. expansion and development of the commercial carp industry in New South Wales. Secondly, the amount of the payment Research on carp impacts and reduces on a sliding scale over three years, control methods providing incentive for the industry to become self-supporting in that time. Thirdly, Current NSW Fisheries carp research projects although an expanded carp fishery will are focused on improving carp management remove greater numbers than the current by: fishery, a reduction in carp numbers is not

104 Bureau of Rural Sciences critical to the success of the subsidy. Rather, Recreational carp fishing the success of the scheme will be determined by the increase in carp catches, and Carp are not only considered to be an under- the increased value of the catch relative to used commercial fishery resource but also an the cost of the subsidy. For these reasons, under-used recreational fishery resource. In the scheme is clearly an industry develop- 1998 a State-wide ‘Great Carp Fish Off’ comment incentive, and distinct from the tradi- petition was sponsored through the CARP tional bounty schemes assessed by Hassall program. Heats were held in 26 regional and Associates (1998). centres across coastal and inland New South Wales, with the finals held on Australia Day. It is unlikely that bounties or incentives for In total several thousand people participated carp harvesting will be any more successful in the event, although not all as competitors, at carp control than those for other verte- and some 34 000 kilograms of carp were brate pests (Section 7.3.1). Irrespective of the caught. This competition may have encour- success of the carp industry development aged recreational carp fishing. However, incentive in expanding the carp fishery in another key aim was to raise community New South Wales, the analyses of Hassall awareness and understanding of the carp and Associates (1998) and Thresher (1997) problem. Recreational carp fishing competi- strongly suggest that commercial harvesting tions are also identified as one method to is only likely to reduce carp numbers in educate the community and foster involve- localised areas. ment in broader land and water manage- The recent restructure of the New South ment activities. Wales Inland Commercial Fishery will result in fishing effort being directed exclusively Broader land and water towards carp and yabbies, when commercial management issues fishing for native species is closed on 1 September 2001. The area open to com- The New South Wales Water Reform Process mercial fishing has been gradually reduced has included a review of water management to around 5% of inland waters over the last policies, provision of environmental flows 50 years (Reid et al. 1997). Seasonal closures for rivers, changes to the pricing, trading and between September and November have allocation of water rights, identification of been introduced to protect mature fish from stressed river and groundwater systems, fishing pressure during the peak spawning funding to improve the efficiency of irriga- period. Closure of this fishery will potentially tion, and increased study and monitoring of expand the areas and methods available to river health through the Integrated remaining carp fishers. Monitoring of Environmental Flows program. A number of other commercial fishers hold permits to participate in small-scale carp Development of the New South Wales Weirs removal projects on behalf of local govern- Policy under the water reform process may ment, other land managers such as provide outcomes which favour native Australian Water Technologies, The species, and which may be detrimental to Centennial Park Trust in Sydney and a retire- carp. In the longer term these and other ment village. Carp populations can be signif- changes may have a significant impact on icantly reduced in relatively small enclosed carp populations. water bodies. Although the success of these NSW Fisheries will review carp research and operations is difficult to measure, land man- management actions to ensure consistency agers are satisfied with the cost relative to with the National Management Strategy for the perceived benefits. Carp Control being developed by the CCCG, and with associated guideline documents.

Managing the Impacts of Carp 105 Current regulations relevant to carp are: The Fisheries Branch of Primary Industries and Resources South Australia (PIRSA), pro- • no size or bag limits exist for carp, nor motes commercial and recreational exploita- are there any seasonal closures tion of carp, and in cooperation with com- • a New South Wales Recreational Fishing mercial fishers, has promoted such fishing to (Freshwater) Licence is required to catch be continued even when densities have been carp in non-tidal or inland waters reduced to levels below those which are commercially viable. Commercial harvesting • an appropriately endorsed commercial is promoted and addressed as a specific man- fishing licence and or permit is required agement option in the management plans for to take carp for sale in New South Wales the fisheries in the Lakes and Coorong • live fish including carp are not to be (Southern Fishermen’s Association 1998). used as bait in inland waters. Efforts are also being undertaken to further develop markets for carp. South Australian Fishers are also encouraged not to return live commercial fishers are also encouraged to carp to the water. promote sustainable harvesting and markets for higher priced native fish species. The Carp management is being developed as one exploitation of all introduced fish species is component of a holistic approach to manag- encouraged. The South Australian Research ing rivers. The New South Wales Water Reform and Development Institute is also attempting Fact Sheet 15 Solving the carp problem (NSW to enhance populations of predatory native Department of Land and Water Conservation fish to control carp. This included a tempo- 1997) summarises the whole of government rary moratorium on the taking of Murray cod approach to carp in New South Wales. (Maccullochella peelii peelii) and the provision of fish passage to reduce fragmentation 6.3.3 South Australia of native fish populations. Chemical poisoning of carp is still undertaken when they are Carp have been successfully eradicated from introduced into watersheds where they have many isolated locations by poisoning (Hall not been previously recorded. A high priority 1988). Between 30 and 120 small popula- is given to the eradication of carp if they are tions have been eradicated, mainly in small detected in new areas such as the Cooper dams in the Adelaide Hills. A major example Basin in the north of the State. of selective harvesting was undertaken using the receding floodwaters of the Chowilla ‘Between 30 and 120 Floodplain (B. Pierce, South Australian small populations have been Research Development Institute, pers. comm. 1998). eradicated.’ Carp are declared an exotic species in South Australia under the Fisheries Act 1982 and it is Wetland management, including measures to illegal for them to be released back into the control carp, is often undertaken by non- water alive or transported. Carp cannot be government agencies. An example of this is held without a permit. Special regulations given in the case study for Pilby Creek have been in place for six years to allow the (Section 8.6.1) where carp have been use of bow and arrow hunting for carp: ‘A removed from wetlands which are moni- bow and arrow may be used during daylight tored to record changes to aquatic vegeta- hours for the taking of European carp in the tion. waters of the Murray River, other than the Carp have been highlighted in the South main stream. This activity may be only under- Australian Recreational Fishing Guide taken when at least 50 metres from all other (1998). Publicity was conducted over one persons not involved in that fishing activity. year to emphasise the benefits of lower carp Note, no other species may be taken by this numbers. This included a major story on method’ (South Australian Recreational ‘River Rabbits’ (Winwood 1996). Fishing Guide 1998).

106 Bureau of Rural Sciences 6.3.4 Australian Capital T erritory for this to occur (M. Lintermans, Environment ACT, pers. comm. 2000). Currently there is a A stocking campaign using golden perch mixed bag limit of ten fish per angler per day (Macquaria ambigua), a predatory native and this includes carp. It is proposed that the species, was undertaken in Lake Burley new fisheries legislation being drafted will Griffin following the establishment of carp in remove this bag limit for carp. It is illegal to the mid 1970s. A similar stocking regime was transfer fish from one water body to another also employed in Lake Ginninderra follow- which limits the potential spread of fish and ing its construction in 1976. Murray cod were diseases. also stocked in both lakes in the late 1970s in a further attempt to develop a substantial There are no commercial fishing operations population of predatory fish but unfortunate- in the ACT although expressions of interest ly neither species appears to have had much have been received for commercial harvest- impact on carp populations (Lintermans and ing of carp. Commercial operations for carp Ruzou 1990, 1991). have not been supported by Environment ACT because of the lack of suitable locations ‘Environment ACT has promoted for such operations and the potential angling for carp in Canberra’s impacts on non-target species. urban lakes with many large 6.3.5 Tasmania fishing competitions organised since the late 1970s.’ Carp are reported to have been introduced to Tasmania in the mid-nineteenth century but there is no evidence of any established Environment ACT manages the catchment of populations from these introductions (Diggle Googong Reservoir in adjacent New South and Jarvis 1998). Carp were found in several Wales and has been successful in preventing isolated farm dams in the north-west of the establishment of carp in this reservoir. Tasmania in the 1970s and were thought to This has required the eradication of carp have been established from Boolara stock. from several farm dams in the catchment as The eradication of these carp using rotenone well as a public education program of the poisoning was undertaken by the Inland benefits of keeping Googong ‘carp-free’. Fisheries Commission (IFC). This swift action Environment ACT has promoted angling for prevented the spread of carp from those carp in Canberra’s urban lakes with many locations (Sanger and Koehn 1997). In 1980, large fishing competitions organised since carp were found in the Stowport area and the late 1970s. Methods for preparing and again were successfully eradicated. In 1995, cooking carp have been promoted. A rela- carp were found in two lakes in the central tively recent development has been the highlands, Lake Crescent and Lake Sorell advent of coarse fishing competitions, with (Section 2.2.8) prompting the immediate Environment ACT providing exemptions for organisation of the ‘Carp Management such competitions in regard to rod limits and Program’ (Diggle and Jarvis 1998) within the keeping fish in keep nets. IFC to undertake carp management. This program team reports to a ‘Carp Working ‘Commercial operations for carp Group’ comprising State government depart- have not been supported mental representatives. because of the lack of suitable Carp are declared as ‘controlled fish’ in the locations for such operations noxious fish provisions under Sections of the and the potential impacts on Fisheries Act 1995. The current provisions non-target species.’ were declared prior to the recent discovery of a reintroduction of carp into Tasmania in 1995. Under these provisions a person may Carp are not declared noxious in the ACT not possess, control, consign, convey or under the Fishing Act 1967, but new fisheries release carp. The IFC must be notified of any legislation recently tabled contains provisions

Managing the Impacts of Carp 107 possession of carp and any IFC officer may closure of the lakes to fishing, the provision seize, remove and destroy any controlled fish. of an inspector to ensure compliance and A person must comply with any direction by capital works to assist management. Works the Commissioner in relation to these matters. have included the installation of screens (Section 7.3.7) to attempt to prevent the ‘The strategy is to keep the lake downstream spread of both eggs and fish, level below the marshes over the and earthworks and the restructuring of out- summer and hence not provide let facilities have been undertaken so that access to potential spawning lake levels can be manipulated. areas.’ Data collected during the 1997–98 summer suggest such manipulation may have contributed to unsuccessful spawning. The strat- The strategy for carp management in egy is to keep the lake level below the Tasmania, following their recent reintroduc- marshes over the summer and hence not tion, is one of containment and population provide access to potential spawning areas reduction, and ultimately eradication if pos- (IFC 1999). sible. The IFC has undertaken a detailed study of the options for eradication of carp in Population estimates indicate there may only Tasmania. Other management options have be 350–400 adult carp remaining in Lake included further surveys to determine the Crescent with an estimated 90% of the popu- extent of the distribution, removal of carp by lation (4572) having been removed. electrofishing and netting using radiotracked Radiotracked carp have allowed information ‘Judas’ carp (over 6355 fish to date) (IFC to be collected on their habitat preferences 1999), research into carp populations, the throughout the year and also enabled the

Outlet weir from Lake Sorrell showing flow-through screens and trap which have been constructed to restrict carp movement. Source: A. Brumley, East Gippsland Institute of TAFE.

108 Bureau of Rural Sciences detection of carp aggregations, enhancing Recently, there has been some concern in the number of fish which can be captured the dairy industry of south-western Western (IFC 1999). A total of 1796 juvenile fish have Australia because carp in farm dams are also been removed, with an estimated 1500 being reported to increase water turbidity. remaining. The total remaining carp popula- Many of the dams are used as a source of tion in Lake Crescent is thought to be less clean water for washing down dairy sheds than 1900 individuals. and thus the water needs to meet quality standards. Many dairy farmers now have to Lake Crescent remains closed to fishing treat the water with flocculants to remove whilst Lake Sorell was re-opened for the suspended matter (G. Robertson, Agriculture 1995–96 season. Since the discovery of carp WA, pers. comm. 1999). in Tasmania, the IFC publication ‘On the Rise’, has devoted extensive coverage to carp in these two lakes. Media coverage of this ‘Education has concentrated introduction of carp into Tasmania has been on public information to raise widespread. awareness to prevent the spread of carp.’ 6.3.6 Wester n Australia There is growing concern about the impact Fisheries WA intends to adapt the Bureau of of carp on the aquatic environment in south- Rural Science’s carp management guidelines west Western Australia, although Fisheries and the CCCG National Management WA is equally concerned about the possible Strategy (Section 3.6) and associated docu- impacts of other introduced fish species ments to develop a framework to deal with including goldfish, gambusia (Gambusia the issue of introduced freshwater fish. holbrooki), redfin perch (Perca fluviatilis) and tilapia (Oreochromis spp.). There have 6.3.7 Queensland been some isolated eradications of carp in As carp have only recently expanded their the past but there is no commercial fishery or range into Queensland in substantial num- widespread removal. bers, mainly through their spread in the Carp are not declared noxious and there is no Murray–Darling Basin, past management specific carp policy although there is general actions have been minimal. agreement that further spread is undesirable. Carp are declared ‘a noxious fisheries Fisheries WA has established a reporting sys- resource’ in Queensland under Part 11, tem linked to a database, and has recently Section 74 of the Fisheries (Freshwater) prepared a public information kit to help Management Plan 1999. Provisions under identify introduced freshwater pests. the Fisheries Act 1994 relating to ‘a noxious Licences are issued for individuals to produce fisheries resource’ include the requirement goldfish for the aquarium trade and some to destroy and notify an inspector of any public confusion remains about how to dis- such resource within two days of taking pos- tinguish between goldfish and carp. session and prohibition on bringing or caus- Carp management is minimal although there ing such resource to be brought into are frequent public requests to Fisheries WA Queensland. Possessing, rearing or selling for their removal from water bodies. It is an carp, releasing, placing or causing carp to be offence under the Fisheries Act 1994 to released into Queensland waters is illegal. translocate any fish without the approval of This makes it an offence to possess carp in the Director of Fisheries. A publicity cam- Queensland either alive or dead. The inten- paign was undertaken in 1997 regarding the tion of this is to prevent any intentional or policy of not allowing translocations of fish unintentional transfer of fish or eggs. It is into or within Western Australia. The exam- currently proposed that the legislation be ple of the spread of carp in the eastern States amended so that it is not an offence to pos- and Territories was used as an example of sess dead noxious fisheries resources. Thus a the need for this. recreational angler would have to kill any captured noxious fish such as carp.

Managing the Impacts of Carp 109 The responsibility for managing carp in (CCC) for the Control of Exotic Pest Fish that Queensland lies with the Queensland meets three times a year. This committee is Fisheries Management Authority (QFMA). made up of government and community Aspects of carp management are undertaken representatives. The CCC has released an by the Department of Primary Industries education and extension strategy which is (DPI) on behalf of QFMA. As carp are now currently being implemented (B. Kerby, widespread, eradication is not currently Queensland Fisheries Management being attempted, but efforts would be made Authority, pers. comm. 2000). to prevent any expansion of its range. To date the QFMA has not received any formal applications to commerically harvest carp. Any such applications would be considered under the QFMA's Exploratory and Development Fishing Policy.

‘There is a growth in fishing competitions for carp.’

There is also a growth in fishing competitions for carp where prizes are awarded for the greatest weight of fish. Although these competitions are privately organised, QFMA is supportive of the concept. DPI has included carp in extension activities and posters regarding other introduced fish species which alert the public to their presence, legislation and potential impacts. DPI is developing a State Strategy for the Control of Exotic Pest Fish due out in 2000. There is also a Community Consultative Committee

110 Bureau of Rural Sciences 7. Techniques to measur e and manage impacts and abundance

Summary impacts of carp. Data from long-term monitoring are needed to evaluate the effective- Estimates of carp abundance are normally ness of carp management programs. only general indicators of actual numbers or densities. The extra effort required to obtain accurate estimates of total numbers is 7.1 Estimating carp abundance rarely justified. Carp abundance can be estimated from catches from recreational Methods for estimating the abundance of fishing events, commercial fishery statistics, carp (Cyprinus carpio) generally fall into biological surveys using an array of sam- one of two categories: (1) estimates of abso- pling gear, mark–recapture and sequential lute abundance to measure the total number depletion methods. of fish in a particular site; or (2) estimates of Impacts of carp are often indirect and can relative abundance to provide an index of be associated with other disturbances in the carp numbers which can be used to compare catchment. Detection of carp impacts can be populations at different sites or at different made difficult by the lack of information times. Although estimates of relative abun- from similar areas without carp. A better dance are typically less precise, the addition- approach is to assess the reduction in carp al cost of estimating total numbers of fish impacts by comparing habitats in which with accuracy is rarely warranted for popula- carp are being managed against similar tion management. habitats in which carp are not managed. The decision to measure absolute or relative However, the presence of other disturbances, abundance is commonly influenced by the critical thresholds and natural stabilising management goals and the spatial scale of influences means that even after carp interest. For example, estimating the total removal, the habitat or native fish popula- number of carp in a small pond may be tions may not return to the condition they important to determine the likely ease or dif- were in before invasion by carp. ficulty of removing all the fish. However, Impacts and abundance of carp can be with large areas such as the Murray–Darling reduced by: capture and removal of carp, River system, an index of carp numbers, and environmental rehabilitation, environmen- where they occur in the greatest densities, is tal manipulation, food chain manipulation, sufficient to determine appropriate control application of poisons, and carp exclusion actions. devices. Potential future biological control Estimates of carp abundance are needed to methods such as diseases, bio-vectored fertil- identify suitable management strategies and ity control and molecular control approach- to monitor the effectiveness of carp manage- es require further development and it is too ment programs. early to assess their value for reducing carp impacts. Existing carp control methods are 7.1.1 Methods for estimating carp relatively affordable on a small scale, but rapidly become too expensive to apply across abundance the entire range of habitats in which carp Carp often live in turbid waters, so that direct are found. observation techniques usually cannot be Monitoring carp populations and their used. Instead, relative carp abundance is impacts is an essential part of a carp control usually estimated from data on catch-per- program. Monitoring must begin before the unit effort. These data come from recreation- management program is implemented, and al fishing catches, commercial fish catches should be scientifically designed to max- and standardised biological surveys. Catch imise the ability to detect reductions in the

Managing the Impacts of Carp 111 tion changes in areas fished. As an example, NSW Fisheries organise ‘Basscatch’ competitions in coastal rivers to monitor the condition of Australian bass (Macquaria novemaculeata) populations. If similar events are to provide reliable data on changes in carp populations, it will be necessary to standardise each year’s catch data for differences in angling ability and hours fished. These factors make correct interpretation of angling catches difficult. Careful attention to quality control is needed to obtain good data over a number of years to quantify differences not related to population size. As an example, the results of Basscatch events conducted by NSW Fisheries in the Hawkesbury River over seven years since 1988 are shown in Figure 17 (J. Harris, NSW Fisheries, unpublished data, 1997). The Standardised information on carp population catch-per-unit effort, measured as fish per variables, including density, age, weight and sex, is angler hour, shows a variable, but relatively needed to determine the impacts of different population stable population of Australian bass after the structures and the effectiveness of management first competition. Importantly, the average programs. Source: A. Toovey, NSW Fisheries. length of fish caught shows that bass are surviving longer and growing to larger sizes rates and total catches achieved by all meth- since the adoption by anglers of a catch-and- ods can be greatly affected by prevailing release philosophy coupled with size limit conditions. For example, gill nets and drum and bag limit restrictions. Properly organised nets rely on fish swimming into the net, with carp competitions may provide similar infor- the result that these methods catch more fish mation on changes in carp populations. during the times of greatest fish movement. Beyond estimates based on simple numbers ‘To provide reliable data on of carp, it is also useful to know the total changes in carp populations, it weight, or biomass, of carp in an area. The will be necessary to standardise impacts of 1000 juvenile carp weighing 50 each year’s catch data for grams each feeding in the water are likely to be quite different from the impacts of 10 differences in angling ability and adult carp weighing 5 kilograms each feed- hours fished.’ ing extensively from the sediments, even though the total biomasses are the same. Current public carp fishing competitions, Consequently, it is necessary to estimate popularly referred to as ‘carp-a-thons’, typi- both the number and biomass of carp in a cally have little control over factors such as habitat to estimate likely impacts. methods used, baits, line types, angler experience and fishing effort. Consequently, Hook and line catches can vary greatly between events for reasons that have nothing to do with the size Recreational fishers commonly catch carp by of the carp population, making this type of hook and line, either intentionally or while competition of limited value in assessing targeting other species. In organised fishing changes in carp populations. In contrast, sci- competitions, the numbers and size of carp entifically planned angling events that con- caught and the fishing effort can be recorded trol many of the variables associated with over a number of years to estimate popula- angling, can be invaluable stock assessment

112 Bureau of Rural Sciences Nets and traps 3 October Nets are commonly used by commercial fish- February 2.5 ers and researchers to catch carp (Figure 18). Gill nets catch fish that swim into the net and become wedged in the meshes of the net. 2 Drum nets are a form of cone trap designed to catch fish, usually as they swim upstream. 1.5 Fyke nets are a smaller form of cone trap that usually contains more internal cones than 1 drum nets. Seines are long rectangular net panels with a small mesh to prevent targeted C/f (fish per angler hour) 0.5 fish from becoming wedged in the meshes, and are towed through the water to either

0 enclose a school of fish or to drag them onto 1234567891011121314 the bank. Some seines have a pocket to help Basscatch event retain fish as the net is pulled through the (a) water. Commercial fishers use gill nets, a drum net or seines to target carp.

250 October Researchers use these methods as well as February fyke nets and various other traps. The size of fish caught using most of these methods is 200 largely determined by the mesh size of the nets used, with larger meshes catching the

150 larger fish whilst allowing smaller fish to slip through. Therefore, estimates of carp abundance may need to use a range of methods 100 and mesh sizes to sample all sizes of carp.

Mean length (mm) Because these methods vary in the sizes and numbers of fish that they catch, catch data 50 need to be adjusted to account for these differences when estimating the total size distri- 0 bution of carp in populations sampled. 1234567891011121314 Basscatch event ‘Constant catches, (b) despite decreasing fishing effort Figure 17: (a) Stable catches of Australian bass by over the last ten years, may indi- anglers in the Hawkesbury-Nepean River system cate an increase in carp num- indicate a relatively constant population over seven years. (J. Harris, NSW Fisheries, Unpublished data bers in the waters open to 1997). commercial fishing.’

(b) Changes in size of Australian bass in the Hawkesbury-Nepean River system, based on anglers Commercial catch records are routinely kept catches, indicate improved growth and survival. by State fisheries agencies and can some- (J. Harris, NSW Fisheries, unpublished data 1997). times provide a longer time-series of information on individual species than are avail- exercises for monitoring carp populations. able from other sources. Catches of carp in With careful planning and commitment by New South Wales increased dramatically fol- participants, carp angling events provide lowing the record floods in 1974–75 to a excellent opportunities for local scale partici- peak of 548 tonnes in 1977–78, and since pation in carp population monitoring. then have remained at relatively stable levels of around 150 tonnes per year (Figure 19; Reid et al. 1997). The fishing effort in New

Managing the Impacts of Carp 113 GILL NET Floats

Float line

Lead line Anchor weight

Funnel DRUM NET Funnel Cod end Wing

Tail post

ENTRY DIRECTION Spreader posts OF WATER FLOW

Wing Hoops

SEINE

BEACH

Hauling ropes

Headline

Leadline

Figur e 18: Diagram of gill net, drum net and seine used to catch carp.

114 Bureau of Rural Sciences South Wales declined dramatically after a both methods are selective towards larger peak in 1977–78, and continued to decline fish. Consequently, catches obtained from from 1985–86 to 1995–96. Constant catches, these fisheries need to be interpreted with despite decreasing fishing effort over the last caution because they do not represent the ten years, may indicate an increase in carp entire carp population in an area or river sys- numbers in the waters open to commercial tem. Because carp live in a wide range of fishing. river, creek, floodplain, billabong and lake habitats, a true index of their relative abun- Stratified habitat sampling dance and size distribution in a river system can only be obtained by sampling all habitats One of the shortcomings of using recreation- and size classes using a stratified survey al or commercial fisheries data to estimate design. This approach is normally undertak- carp abundance is that these fisheries typi- en independently of a fishery and usually cally operate only in selected habitats suited provides a useful check on fishery-based to the types of gear used. Another is that information.

600

500

400

300

200 Catch (tonnes)

100

0 47–48 53–54 59–60 65–66 71–72 77–78 83–84 89–90 95–96

(a) Year

350

300 Number of boats Number of fishers 250

200

150

Number of fishers/boats 100

0 53–54 59–60 71–72 68–69 77–78 83–84 62–63 65–66 80–81 92–93 95–96 89–90 50–51 56–57 86–87 47–48 74–75

(b) Year

Figur e 19: Carp catches (a) and changes in fishing effort (b) in New South Wales from 1947–48 to 1995–96 (Reid et al. 1997).

Managing the Impacts of Carp 115 Electrofishing electrofishing is generally only used by research teams or approved operators who While no single fishing method is equally are trained to minimise damage to fish. effective in all habitats, electrofishing is an Because it requires the use of high voltage effective method in a greater range of habi- electricity in and around water, electrofish- tats than other methods and also catches fish ing equipment is highly specialised and rela- of all sizes, although larger fish are more sus- tively expensive. The risk of injury to both ceptible. Compared to netting and angling operators and observers is such that an methods, electrofishing is less influenced by Australian Code of Electrofishing Practice changes in carp behaviour associated with has been established and was approved by seasonal temperatures, river flows, feeding the Ministerial Council on Forestry, Fisheries and reproduction. and Aquaculture in 1997. ‘Electrofishing is effective in a Electrofishing is generally not species-specif- greater range of habitats than ic. This means that all fish species and other aquatic vertebrates in the electric field may other methods.’ be affected. By adjusting the voltage, frequency, duty cycle, shape of the output Electrofishing uses an electric current (most wave and the method of applying current to commonly pulsed direct current) in the the water, it is possible to increase selectivity water to create an electric field which attracts for larger or smaller fish to some degree. and immobilises the fish so they can be easi- However, contrary to popular opinion, there ly removed from the water. Electrofishing is no ideal combination of settings that catch units can be powered by a generator in a only one species, such as carp. boat or mounted on the shore, or by a bat- tery or generator attached to a backpack Other methods unit. The effectiveness of electrofishing is strongly influenced by the type of current Somewhat more novel, high-technology used, the shape of the output wave and the methods of estimating carp abundance are output frequency, as well as the conductivi- video and sonar-based techniques. Fish ty, turbidity and temperature of the water counters can be installed at strategic sites, and the behaviour patterns of different fish such as fishways, where images of fish pass- species. ing a fixed point can be identified to species and counted over time. This technique has Although electrofishing attracts fish, like potential to provide accurate numbers of most other fishing methods, it can potentially carp migrating upstream past key points in cause injuries. Most common injuries are river systems but is still under development compressed vertebrae or haemorrhages and not yet widely available. Similar tech- caused by excessive muscle contractions. niques based on sonic imaging using side- The risk of damage to native fish means that scan sonar also enable numbers of carp and other species to be estimated without the need to catch fish. To be most useful, these methods need to be linked to image recogni- tion software that distinguishes between different species and provides separate counts for each species detected. The difficulty in developing new software, or in recalibrating existing software to recognise Australian species, has prevented the widespread adoption of this technology in Australia. Hybrid methods combining two or more established methods for catching fish can Electrofishing allows relatively selective sampling and removal of carp. Source: J. Koehn, Department of sometimes be highly effective. For example, Natural Resources and Environment, Victoria.

116 Bureau of Rural Sciences combining seine nets with electrofishing Box 3: Estimating carp abundance: technology has resulted in electric seines single mark–r ecaptur e which are currently being evaluated by NSW Fisheries for their effectiveness in catching method carp (C. Schiller, NSW Fisheries, pers. comm. 1999).

7.1.2 Estimates of absolute abundance Absolute carp abundance can be estimated using two well-established techniques commonly used in fisheries management: mark–recapture and sequential depletion.

Mark–recapture methods Mark–recapture techniques rely on a known number of individuals being captured, marked and released. The proportion of marked individuals in a second sample can then be used to estimate the total number of fish in the population (Box 3).

Sequential depletion methods Sequential depletion methods work by repeated sampling of a known habitat, without replacing caught fish. Catches commonly decline with consecutive samples, enabling the total number of fish to be estimated (Box 4) (Reid and Harris 1997). In isolated habitats such as wetlands, weir pools or water storages, draining the water from the habitat for ecological or operational reasons often strands significant numbers of carp, allowing numbers to be estimated or counted. Similarly, chemical treatment of water storages can sometimes cause fish kills, enabling total numbers of carp to be estimated, as can the targeted use of piscicides.

7.2 Measuring the impacts of carp on the envir onment

Many factors make it difficult to accurately assess the impacts of carp. Changes in land use, run-off and sedimentation, clearing of bankside vegetation, stock access and altered river flows all contribute to some of the impacts also attributed to carp, such as bank erosion and slumping, and increased turbidity (Chapter 5). Some assessments of

Managing the Impacts of Carp 117 Box 4: Estimating carp abundance: carp impacts can be made by comparing environmental variables between habitats sequential depletion method with high densities of carp and those with low carp densities. However, carp impacts can be difficult to distinguish from other dis- Hypothetical example: A small, closed population is turbances in this form of comparison unless sampled eight times without replacement. The results are the sites are chosen carefully to eliminate as follows: potentially confounding sources of variation. 16 Alternatively, sections of a habitat may be fenced off with fine-meshed netting to 12 exclude carp (King et al. 1997). Comparison over time of habitat conditions between 8 nearby carp exclusion and non-exclusion zones may enable changes directly

No. of fish caught 4 attributable to carp to be estimated. A variation of this approach is to use multiple dams 0 or billabongs in similar condition and to 12347 568 reduce carp numbers in some of them. The exclusion method has a potential drawback Samples in that by excluding carp, other fish and ani-

Because of the small size of the population and the zero mals may also be excluded, which may lead results in the last 2 samples, we can assume that the whole to other changes not caused by carp. Despite population has been sampled. Abundance calculation is this complication, large differences in water simplified as the sum of the results of all samples. Hence: 15+12+10+7+3+1+0+0= 48 quality, sediment disturbance and growth of aquatic vegetation have been observed in However, sampling a much larger population reduces the experimental ponds and billabongs where accuracy of such a calculation. carp have been excluded (Section 5.3). Example: Carp larger than 100 millimetres in the Bogan Another difficulty in assessing carp impacts River, New South Wales. Source: Reid and Harris (1997). occurs in rivers where carp can move over 200 large distances. In contrast to standing waters with closed populations, carp in 150 rivers are able to move upstream or downstream so that the population at any one site 100 might vary greatly during the period of measurement. In such cases, even though a dif-

No. of fish caught 50 ference might be detected between carp exclusion zones and non-exclusion zones, it 0 12345 can be difficult to attribute changes to carp unless carp numbers in the non-exclusion Days sampled zone are known at the same time.

In this example, carp were caught and removed from the Bogan River in New South Wales on five consecutive ‘Studies are most likely to be days. The carp population was estimated using the same useful in areas where carp do principles as the above example, but using a more complex statistical method in the computer program not yet occur and where they CAPTURE (Otis et al. 1978). The size of the carp might be expected to occur population in this section of river was estimated to be 868 individuals, with 95% confidence limits from 808 to 947 within a few years.’ fish. None of these difficulties make it impossible to measure impacts of carp in aquatic systems, but failure to address potential sampling problems can result in large expenditure of time and money for results that cannot be properly

118 Bureau of Rural Sciences Box 5: Befor e-After-Contr ol-Impact Box 6: Differ ences between impact (BACI) and r ecovery studies

The simplest form of Before-After-Control-Impact design The changes that occur following carp removal may be looks for differences between sites with carp (Impact) and different from those that occurred after the introduction of without carp (control), before and after carp have been carp. This can reflect other changes since the introduction introduced. The analysis compares groups of sites of carp, such as catchment disturbance, clearing arrowed. Under ideal conditions, there would be little vegetation, desnagging, altered river flows and changes difference between sites BC and BI, and little difference in water temperatures. Environmental variability will also over time between treatments BC and AC. If changes influence how a system stabilises after carp have been between BI and AI, or between AC and AI, are greater removed. In the first example below, the habitat conditions than changes between BC and BI, or between BC and and fish community following carp removal are quite AC, then an impact caused by carp has been detected. different to the situation before carp became established. This design is often impractical because there are no comparable sites without carp to use as controls, and it is unusual to have useable data from a time before carp were introduced.

Before CONTROL IMPACT carp Carp (no carp) (carp present) removed

BEFORE BC BI CARP INTRODUCED

FISH COMMUNITY With carp

AFTER AC AI HABITAT CONDITIONS CARP INTRODUCED

In other cases, carp removal may allow a system to return to something close to the state that existed before carp Recovery studies may follow the same design, but use became established. A return to near previous conditions disturbed sites with carp as controls, and sites from which is more likely in relatively simple systems where other carp are to be removed as impact sites. The ability to disturbances are minimal. detect either impact or recovery is greatly improved by increasing the number of sites and the number of times sampled before and after removing carp.

DISTURBED RECOVERY (with carp) (carp removed) Before Carp carp removed

BEFORE CARP BD BR REMOVED

With FISH COMMUNITY carp

AFTER CARP AD AR REMOVED HABITAT CONDITIONS

The arrows signify the direction of change in either a spatial scale (for example control impact, disturbance recovery) or temporal scale (before after).

Managing the Impacts of Carp 119 interpreted. Powerful statistical methods now embarking on a program in order to max- used widely to detect environmental impacts, imise the ability to detect real changes result- adopting Before–After–Control–Impact (BACI) ing from efforts in carp control. and related experimental designs (Underwood 1996; Box 5), still have several 7.2.1 Water quality limitations in detecting impacts caused by carp. Importantly, it is often impossible to Increased turbidity is the main aspect of study the condition of habitats before carp water quality most commonly attributed to became established. If control sites without carp. But the turbidity of a water body can carp are fundamentally different from sites change because of high flows, sediment with carp, the comparison between sites is inputs from run-off or through wind and meaningless in relation to carp impacts. For wave action disturbing sediments. The size these reasons, BACI studies are most likely to of sediment particles also influences the rate be useful in areas where carp do not yet occur at which they settle out, so that neighbouring and where they might be reasonably expected billabongs may show differences in turbidity to occur within a few years. simply because of different sediment com- positions (King et al. 1997). In the study by Recovery studies provide an alternative to King et al. (1997), carp increased turbidity impact studies. Instead of attempting to outside the range normally encountered in detect the impact of a disturbance such as billabongs without carp, although wind and carp, recovery studies remove the source of sediment run-off may also have contributed. disturbance, that is, carp, and the investiga- Turbidity varies naturally along the course of tion focuses on detecting recovery from dis- a river and over time. For example, in five turbance (Roberts and Ebner 1997). This billabongs near Albury studied between form of assessment is free of many of the 1982 and 1986, turbidity averaged 23.1 constraints of assessing the impact of an Nephelometric Turbidity Units (NTU) and introduced population of carp, and has been ranged from 0.9–217.5 NTU (Boon et al. applied successfully in Australia (King et al. 1990). Flow conditions dramatically affect 1997; Robertson et al. 1997). Recovery stud- turbidity, with floodwaters picking up large ies can be planned to suit most accepted amounts of fine particles upstream, and experimental designs for impact assessment, depositing them further downstream as the and are particularly valuable in demonstrat- water velocity slows. ing the benefits of management actions to reduce carp (Roberts and Ebner 1997). Turbidity can be measured with readily However, there is an important distinction available electronic meters. However, there between impact and recovery studies. The are two distinct components of turbidity with changes that occur after carp have been respect to carp. Sediments stirred up by removed are not necessarily the reverse of feeding carp contribute directly to turbidity. the changes that follow carp introduction. Algal turbidity may also increase as a result Environmental variability and other forms of of carp activity, through nutrients released disturbance may result in habitat conditions from the sediments or from excretory prod- following carp removal that are noticeably ucts. To assess changes in turbidity different from the conditions that existed attributable to carp control, it is desirable to before carp (Box 6). Futhermore, ecosystem obtain separate measurements of these dif- components that may have been affected by ferent sources of turbidity. carp, such as seedbanks of aquatic plants, may not recover without active intervention 7.2.2 Other factors to re-establish pre-impact conditions. Other environmental factors associated with Reliable detection of environmental impacts carp impacts are sediment deposition, phos- and recovery is now a highly specialised phorus availability, substrate pock marks area of ecology and it is strongly recom- created by carp and changes to macrophyte mended that proposals for carp management density (Roberts and Ebner 1997). Harris and be referred for professional advice before Gehrke (1997) suggested that the incidence

120 Bureau of Rural Sciences of external lesions in native fish is correlated for carp management (Section 8.3.3) where with carp density, although this needs to be management of more susceptible and inher- confirmed by further investigation. ently valuable areas with lower carp densities may provide a greater return on invest- Rates of river bank erosion and slumping can ment. Strategies that focus on impact reduc- be measured and associated with carp densi- tion may also prove more effective and eco- ty, but this would need to be examined on a nomic in the long-term compared to ongoing large spatial scale over a relatively long time carp removal. At the same time, carp to detect the contribution made by carp. removal may change the age structure of the Recent investigations of bank erosion and population and therefore the nature of slumping in irrigation channels and in the impacts (Section 3.3.2) and the fecundity of Darling River were either inconclusive remaining fish which may be advantageous. (Roberts and McCorkelle 1995) or suggested that factors other than carp were involved (Thoms 1997). 7.3.1 Captur e and r emoval Most of the impacts of carp are relatively Capture and removal is a common method easy to establish in controlled experiments in for attempting to control some feral animal ponds or billabongs, but the need to conduct species and this approach is also perceived experiments on an appropriate spatial scale as an option for reducing carp populations. makes carp impacts in rivers much more dif- Fishing, in all its forms, is by far one of the ficult to evaluate. Consequently, the true world’s most popular and, arguably, success- impact of carp on flowing water habitats will ful techniques for reducing the abundance of always be difficult to estimate. fish. The history of the fishing industry contains a number of examples of species that Impacts of carp on native fish, through pre- have been fished to dangerously low levels, dation, competition and disease, have been such as gemfish (Rexea solandri) in eastern claimed to occur for some time (see Chapter Australia, southern bluefin tuna (Thunnus 3 and Section 5.3.4). However plausible such maccoyii) in the Indo-West Pacific region, claims may be, there is no direct evidence in and northern cod (Gadus morhua) off the Australia that carp have caused the Canadian east coast. Most of these popula- widespread decline of native fish species. tions, however, inhabit open oceans or Evidence from commercial fishery statistics coastal waters where commercial or recre- shows clearly that native species were ational fishing is one of the few ways that declining in some areas, probably as a result fish populations can be managed (Thresher of fishing pressure and multiple habitat dis- 1997). In contrast, carp live in rivers and turbances, well before carp became estab- lakes of all sizes where methods other than lished (Reid et al. 1997). However it is likely direct removal also allow fish populations to that high carp numbers are now instrumental be controlled. in keeping the number of native fish at a low level (Gehrke 1997a). Direct effects of carp ‘Commercial carp harvesting has through interference competition and exploitation competition can be determined been conducted in the Gippsland by manipulative experiments in both field lakes at signficant levels for the and pond environments. past decade with no apparent reduction in carp biomass.’ 7.3 Population contr ol Carp removal can be achieved through both techniques commercial and recreational fishing, as well Much of the debate about carp management as through dedicated removal operations. centres around population control rather Whilst commercial fishing can remove rela- than impact reduction, particularly for water- tively large numbers from some areas (Section ways in public areas with high carp densi- 5.4.3), it is an impractical form of removal in ties. This focus may hinder seting priorities many areas, especially in inaccessible river

Managing the Impacts of Carp 121 reaches or habitats far from markets, or where the population consists largely of individuals of unmarketable size. The ability of dedicated carp removal teams to reduce carp numbers effectively depends upon the methods which can be used, which often depend in turn on the size and structure of the habitat. Angling is an exceptionally popular pastime in Australia, with many anglers living near or willing to travel to relatively remote areas. Anglers use a wide variety of baits to catch carp, with canned corn, bread crust and boiled potatoes common choices in coun- Some states encourage removal of carp by recreational tries where carp fishing is popular (Spitler line fishing. Source: A. Brumley, East Gippsland 1987). Although the diet of wild carp is Institute of TAFE. based on zooplankton and insects with some plant material, corn products (for example, needed to limit recruitment to low levels canned corn, corn meal, corn syrup, corn (Section 3.4.3). To achieve such a large germ) feature strongly in lists of carp attrac- reduction in carp numbers, the removal effort tants used by anglers. The ability to attract must target all carp habitats, not just those in carp using products that are readily available which carp can be easily caught. Otherwise, to anglers, but which do not occur naturally immigration from unfished areas, combined in their diet may provide options for selec- with compensatory reproduction and sur- tive removal of carp from some habitats. vival, will cause a rapid return to previous However, removal of carp by angling will population levels. In contrast, capture and usually have little effect on carp populations. removal of mature individuals from small The extent to which removal reduces carp populations in confined habitats is likely to populations depends on the scale of the significantly reduce the reproductive capacity removal and the dynamics of the population. of the population. Unfortunately, little is known of the popula- The ability of commercial carp harvesting to tion dynamics of carp populations in have a significant impact on carp popula- Australia and the factors which drive populations even in enclosed waters is question- tion increase in the wild. The natural variabil- able. For example, commercial carp harvest- ity of Australian rivers also makes it difficult ing has been conducted in the Gippsland to predict or model wild carp populations. lakes at significant levels for the past decade Physical removal on a large scale could have (Section 5.4.1), yet it appears sustainable value as a control technique where numbers with no apparent reduction in carp biomass. are already low or where the population is suffering from poor recruitment as a result of Bounty schemes have been used throughout unfavourable environmental conditions. the world as a financial incentive to induce Even in these cases, removal will need to be control of many vertebrate pest species continued indefinitely at levels beyond those (Hassall and Associates 1998). In Australia, which would be commercially viable, bounty schemes or harvesting subsidies have because even heavily fished carp populations been used for pest species including goats return rapidly to pre-fished levels once har- (Parkes et al. 1996), pigs (Choquenot et al. vesting stops (McCrimmon 1968). The target 1996) and foxes (Saunders et al. 1995), but population size required to produce a rela- have often been discontinued as they have tively stable, low population density in the been considered to be of doubtful value as a Murray–Darling River system has been esti- form of pest control (Parkes et al. 1996). In a mated at less than 10% of the unfished review of bounty schemes, Hassall and biomass (Thresher 1997). This estimate is Associates (1998) concluded that most had consistent with the adult population density

122 Bureau of Rural Sciences been condemned by their implementing 7.3.2 Envir onmental r ehabilitation agencies as a ‘costly, misguided and ineffective tool for addressing pest problems’. Whilst physical removal of carp is a direct Reasons have included fraudulent practices method of control, restoring ecological pro- and the failure to provide relief from pest cesses in aquatic ecosystems may impose an impact. Another reason is the targeting of the indirect form of control (Harris 1997). It is pest where they are in the greatest densities accepted that many Australian rivers and and hence where they are the most easily lakes have been severely degraded (Williams caught, rather than where control is most 1980; Harris and Gehrke 1997) and their effective in reducing impact (Whitehouse native fish faunas depleted (Cadwallader and 1977; Saunders et al. 1995; Smith 1990; Lawrence 1990; Harris and Gehrke 1997; Choquenot et al. 1996). Hassall and Gehrke et al. 1999a). Environmental distur- Associates (1998) concluded that bounty bance has been recognised as favouring the schemes were unlikely to result in significant establishment of new species (Tilzey 1980; Li or long-term pest damage reduction. and Moyle 1993) and disturbances to both coastal and inland river systems have been It is unlikely that bounties or incentives for widespread in Australia. Examples of distur- carp harvesting will be any more successful bances include toxic pollution, thermal pol- at carp control than those for other verte- lution and other changes to water quality, brate pests. Irrespective of the success of the destruction or removal of fish habitats, carp industry development incentive in changes to flows including reduced flooding expanding the carp fishery in New South and altered flow variability, and barriers Wales, the analyses of Hassall and Associates which alter both longitudinal and lateral con- (1998) and Thresher (1997) strongly suggest nectivity within river systems. These changes that commercial harvesting is likely to have been demonstrated as having detrimen- reduce carp numbers in localised areas only tal effects on aquatic fauna, especially native and have little effect on the control of carp fish species (Cadwallader 1978; Harris 1984; populations on a wide scale.

Re-establishment of riparian vegetation and improving other aspects of aquatic ecosystems may decrease the competitive advantage of carp over native fish species. Source: A. Brumley, East Gippsland Institute of TAFE.

Managing the Impacts of Carp 123 Koehn and O’Connor 1990a; Gehrke et al. reducing predation pressure on other 1995; Gehrke et al. 1999a). species including carp (Gehrke 1997a). Driver et al. (1997) suggested that improved Aquatic ecosystems with natural levels of river management would be effective in disturbance and with established native fish reducing carp densities, resulting in populations are more resilient to invasive improved water quality and stronger native species such as carp. Adopting an ecosystem fish populations. Suitable management approach to carp control works to re-estab- options include: limiting carp spawning lish the resilience to invasion within the natu- habitat (Section 3.4.2); restricting carp dis- ral system while other strategies focus more persal (Sections 3.4.3 and 3.4.5); reducing directly on reducing carp numbers. Restoring catchment-wide effects of agriculture, such such ecosystem attributes as habitat struc- as siltation and land clearing (Section 3.2.1); ture, bed contours, substrate type, flow and restoring natural flow regimes (Section regime, water quality, aquatic plants, ripari- 3.2.1). Other options to reduce levels of an vegetation and connectivity between catchment disturbance may also limit carp habitats can make conditions less favourable populations in urban areas (Sections 2.1.4, for carp and is likely to enhance native fish 3.5.5 and 6.3.2). numbers. Examples of the types of habitat restoration works that may be undertaken, ‘Aquatic ecosystems with natural focussing on European fish species, are levels of disturbance and with given in Cowx and Welcomme (1998). Many established native fish of these principles can be modified and populations are more resilient to applied to Australian conditions and fish species. invasive species such as carp.’ 7.3.3 Envir onmental manipulation Carp have high tolerances to poor water quality conditions and therefore have a Complete removal of carp can be achieved greater ability to exploit polluted habitats by draining and drying isolated habitats. than many native species (Hume et al. 1983a; Carp have been shown to be less adept at Growns et al. 1998; Gehrke et al. 1999a; returning to the river from off-stream flood Section 3.2.2). They also have broader habi- waters than many native fish species (Koehn tat preferences than many native fish species and Nicol 1998) and often become trapped (Koehn and Nicol 1998). Mallen-Cooper et in these waters. Selective carp removal has al. (1995) (Section 3.2.1) found carp could also been undertaken on the Chowilla flood- negotiate some obstacles that posed serious plain in South Australia through reductions barriers to migrating native fish species. in water levels (B. Pierce, South Australian Reduced variation in flow also favours carp Research and Development Institute, pers. which are more adapted to constant flows. comm. 1998). Measures need to be under- Studies in the Murray–Darling Basin show taken to prevent reintroductions where that carp numbers are higher in catchments anabranches reconnect to rivers. Whilst this where river flows have been most altered is possible for adult fish by using screens, it (Gehrke et al. 1995; Gehrke et al. 1999b). is difficult to prevent smaller fish from re- These factors all favour carp over native fish, entering the cleared habitat, where they may as well as having direct detrimental effects eventually establish another population. on native species by directly modifying their Another form of environmental manipulation habitats, restricting their breeding (Harris involves drawing down the water level in and Gehrke 1994) and limiting their ability to lakes and impoundments to prevent access by recolonise habitats (Harris and Mallen- carp to littoral habitats which offer submerged Cooper 1994). Reductions in the numbers of vegetation for spawning habitats. This large native fish, such as Murray cod approach appears to have been successful in (Maccullochella peelii peelii) and golden Tasmania, although complete data are not yet perch (Macquaria ambigua), have also available (J. Diggle, Tasmanian Inland modified aquatic food webs by severely Fisheries Commission, pers. comm. 1999; Section 6.3.5).

124 Bureau of Rural Sciences 7.3.4 Chemicals Rotenone can be applied to fish by suspen- sion in water, by injection or by ingestion of Poisons have been used to reduce popula- an oral bait. In suspended form, rotenone tions of many terrestrial vertebrate pest enters the fish through the gills as the fish species on a wide scale. However, respire. It is carried through the entire body widespread use of poisons is not possible in of the fish and causes the fish to suffocate aquatic habitats, because species-specific because oxygen in the blood is not released poisons for carp are not yet available to the tissues. In commercial preparations, (Marking 1992) and the risk to non-target rotenone is commonly mixed with a syner- native fish species is unacceptable in most gist which prevents the fish from detoxifying cases. the rotenone. Addition of the synergist means that less rotenone is required to kill ‘The recent discovery of carp in fish. A solvent is also often added to dissolve Tasmania highlights the danger the rotenone in liquid preparations to assist of reintroductions by human application to water. Fish that have not translocation even if eradication acquired a toxic dose of rotenone in their is achieved.’ bodies can be revived by removing them to clean aerated water but once a toxic level has accumulated the fish will die. Potassium Carp have been successfully eradicated from permanganate can be applied to de-toxify isolated waters in several locations using water treated with rotenone but cannot chemical poisoning (Sections 6.3.3 and revive affected fish. 6.3.5). Poisoning is not always effective on a wider scale, however, as was shown in ‘Better knowledge about carp Victoria where carp eventually became biology may enable existing established in the La Trobe River. The recent chemicals to be applied in discovery of carp in Tasmania also highlights the ever-present danger of reintroductions innovative ways that deliver the by human translocation even if eradication is poison to carp without placing achieved. other species at risk.’ Other introduced fish species, such as gambusia (Gambusia holbrooki), redfin perch Rotenone is more toxic to fish in acidic water (Perca fluviatilis), brown trout (Salmo trut- and in waters with low hardness. It is more ta) and rainbow trout (Oncorhynchus toxic at higher temperatures, but also breaks mykiss) have been eradicated from certain down more rapidly, reducing the time of areas by chemical poisoning (Sanger and effectiveness. Sunlight also accelerates Koehn 1997). breakdown of rotenone. Turbidity caused by clay particles in the water can adsorb Only a few products are available for poison- rotenone, effectively reducing its concentra- ing fish. The best known is rotenone. tion. Species such as carp that stir up sedi- Rotenone poisoning has been the method ments can increase turbidity to the extent most widely used by fisheries agencies in that it affects rotenone treatment. Because Australia to remove unwanted fish from rotenone enters the body via the gills and freshwater habitats. Rotenone is produced not across the skin, vertebrates other than from the roots of several different plants, fish have little risk from exposure, except for most commonly derris root (Derris spp.), amphibians (frogs, toads and their tadpoles) which gives rise to the name ‘Derris Dust’ which are highly susceptible. commonly used as a garden insecticide. It is one of the safest pesticides available and is In addition to the powder and liquid forms labelled for use on young domestic pets as a available, rotenone has also been formulated flea powder. It is an organic odourless yel- into baits for oral application and into a form low crystal or powder which is insoluble in that can be delivered by helicopter. When water. applying rotenone, operators should avoid contact with the skin and avoid breathing its

Managing the Impacts of Carp 125 dust or vapour. Exposed areas should be chemicals in flowing waters holds more washed with water for 10–20 minutes. No problems because the chemicals must be human deaths have been reported from broken down or de-toxified to prevent killing rotenone use but it may cause liver damage non-target organisms downstream. and irritate the skin and eyes (Rotenone prod- Unlike most other forms of fish removal, poi- uct information, Prentiss Incorporated, USA). soning has special significance in terms of Other chemical products include endosul- public perception, the risk of downstream fan, antimycin, acrolein and copper sul- kills and the effects on other fish species pre- phate, with each having advantages and dis- sent. The prospects for large-scale use of advantages. These chemicals were devel- rotenone or other poisons are limited. The oped for purposes other than poisoning fish cost, and availability of rotenone, environ- and are not approved for use as fish poisons mental risks and problems of ensuring a in Australia, although fish kills resulting from complete eradication whilst eliminating the their use have been reported. Application of risks of reintroduction all weigh against this copper sulphate to Wingecarribee Reservoir, method of removal. Mass kills of carp could south-west of Sydney, in December 1997 to also pose pollution problems and this is an control nuisance algae resulted in the death issue for other potential lethal techniques of approximately 15 000 carp (P. Gehrke, including viruses and fatality genes. NSW Fisheries, pers. comm. 1998). Research However, rotenone application may be read- is continuing into other applications with ily justified as a rapid response to control new fish management baits and alternative carp outbreaks beyond their current distribu- preparations being developed in North tion. Small-scale use of rotenone will contin- America (Sanger and Koehn 1997). ue in controllable environments such as farm dams and small reservoirs. Larger reservoirs The use of chemicals is often controlled by may be treated more cost-effectively when environmental regulations which over-ride water levels are low. fisheries agencies and so their use must be well justified. This provides environmental Novel uses of rotenone, such as baits pre- safe guards against unauthorised use of pared to improve species selectivity, require chemicals, but delays could prove critical if further development and testing. Prentiss potentially controllable populations spread Incorporated in the United States market a before permission is given and action is rotenone-based bait to control grass carp taken. The use of poisons also causes (Ctenopharyngodon idella), and are devel- widespread public concern and can be a oping a similar product for carp which is not high-risk strategy unless well planned and yet commercially available. It is unlikely that implemented. chemicals will be identified that are selective to carp alone. Better knowledge about carp The application of chemicals in small isolated biology and physiology may enable existing waters such as farm dams is relatively approved chemicals to be applied in innova- straightforward as there is little chance of a tive ways that deliver the poison to carp spill and neutralisation of the chemical can without placing other species at risk. be allowed to occur naturally. Large-scale rotenone treatments in reservoirs have been conducted worldwide, with the most notable 7.3.5 Viral contr ol agents examples coming from the United States Biological control of carp with a virus was (Sanger and Koehn 1997). A recent review suggested during the rapid spread of the found that about 48% of large-scale rotenone species during the 1970s. The agent suggest- applications had achieved their goal ed was Spring Viraemia of Carp Virus (SVCV) (Meronek et al. 1996). The largest document- (Rhabdovirus carpio) which causes a haem- ed application in Australia was in Leigh Creek orrhagic disease that had been isolated in Retention Dam in South Australia (Hall 1988) farmed carp in Europe (Crane and Eaton where the dam was successfully treated with 1997). The possibility of using SVCV as a bio- rotenone to kill carp and prevent their escape logical control agent was also raised at carp into the Cooper Creek system. The use of forums held in 1994 and 1995 (Hindmarsh

126 Bureau of Rural Sciences 1994; Crane 1995). To date, consideration of the Biological Control Act 1984. Such autho- the use of viral control agents has focussed risation could give indemnity against legal almost exclusively on SVCV. action for compensation to the agency that released the virus. Compensation might oth- In order to assess the potential of such a erwise be claimed by commercial carp har- method of biological control it is important vesters and processors and others who profit to understand its functioning and limitations. from the presence of carp in Australia. As All rhabdoviruses isolated from fish are cur- Spring Viraemia of Carp Disease is a notifi- rently considered to be exotic to Australia. able disease in Europe, its release in As carp in Australia originated from Europe, Australia would mean that Australia would it is possible that SVCV may already be pre- no longer be considered free of the virus, sent in this country (Crane and Eaton 1997). which may have implications for trade in Spring Viraemia is considered to be a disease ornamental fish (Crane and Eaton 1997) or of farmed carp and is rarely observed in wild fish products. populations. It can affect carp of all ages and exhibits clinical signs that are typical of any systemic infection: pale gills, haemorrhages, 7.3.6 Biomanipulation dark skin colouration, abnormal swimming Biomanipulation is the practice of deliberate- and depressed respiration. Mortality is usually manipulating the interrelationships among ly in the range of 20–40% although it may plants, animals and their environment to reach 100%. Most, if not all, cyprinid species achieve a new ecological balance. This is are likely to be affected to some degree by usually attempted in lakes to control prob- this virus (Crane and Eaton 1997; Section lems such as aquatic plants or algae. For 3.4.4). Consequently, other cyprinids cur- example, recurrent algal blooms can some- rently in Australia would also be at risk if the times be controlled by increasing the density virus were released. of grazing zooplankton. Simplified stages of biomanipulation that involve fish are: (1) ‘Intense scrutiny would be given reducing populations of zooplanktivorous to the release of viral control fish to low levels, and (2) stocking the sys- agents, especially those which tem with predators to suppress subsequent may be water-borne.’ growth of the zooplanktivorous fish population. While a single manipulation may result in a stable system, either or both phases may The effects of SVCV on carp populations need to be repeated annually or on an ad under Australian conditions are not known. hoc basis to maintain the desired balance. Improvements to carp farming conditions in The goal of the exercise is to change a sys- Europe, including reducing fish stress, have tem from an undesirable steady state to reduced mortalities caused by SVCV. There another, more desirable, steady state that will appears to be little environmental stress on not revert readily to its previous condition. wild carp populations in Australia, even The concept of biomanipulation is directly though carp populations here may not have relevant to reducing the environmental been subjected to the virus before. In the impacts of carp in closed systems such as Murray–Darling Basin, carp are not subjected lakes and ponds. However, it is much more to severe, cold winters, spring is relatively difficult to achieve a desirable, managed out- short and summers are long and hot, all con- come by manipulating the food chain in ditions which are not particularly favourable flowing-water environments. to this virus (Crane and Eaton 1997). Several overseas studies have shown reduc- Following the public controversy surround- tions in the recruitment of cyprinids following the release of the rabbit calicivirus, ing stocking with predatory pike (Prejs et al. intense scrutiny would be given to the 1994; Berg et al. 1997). Whilst stocking release of any further viral control agents in Australian waters with such introduced Australia, especially those which may be predatory species is not a sound ecological water-borne. Authorisation for its release option, the use of native predatory species would almost certainly be required under

Managing the Impacts of Carp 127 may be likely to have similar effects and war- populations via a biomanipulation exercise rants serious scientific evaluation. difficult because carp from other areas can rapidly replace those removed. It also ‘Biomanipulation control of carp requires much higher stocking densities of requires habitat restoration to predators to replace those which emigrate. support native species, the The decline of most native fish populations ability to reduce carp numbers in south-eastern Australia began as a result of exploitation and habitat changes before to a low level, and the ability to carp populations expanded. Stocking large greatly increase numbers of numbers of fish into riverine habitats which predators.’ can no longer support large populations is more likely to further destabilise the system, Although predation on carp, especially with unpredictable and potentially undesir- young fish, by predatory native fish such as able results, than it is to effectively control Murray cod and golden perch occurs, no sci- carp. For biomanipulation control of riverine entifically conducted trials have been under- carp populations to be effective, substantial taken to ascertain the potential of this habitat restoration to support native species, method for controlling carp. Native fish the ability to reduce carp numbers to a low species are stocked mainly for species con- level, and the ability to greatly increase num- servation and to support recreational fish- bers of predators without destabilising the eries by fisheries agencies in Queensland, system, are essential pre-requisites. The New South Wales, the Australian Capital capacity to implement these changes cur- Territory and Victoria. The added advantage rently exists only for very small rivers in iso- of carp control from these stockings is often lated catchments. mentioned, although not evaluated. Because carp recruitment in large populations is likely 7.3.7 Carp exclusion devices to be density-dependent, and because large In contrast to methods for controlling carp mature carp have very few predators in impacts by reducing the size of existing popu- Australia (Section 3.4.4), predation on small lations, carp exclusion devices are intended to carp is unlikely to have any appreciable prevent carp from establishing populations effect on adult carp populations. Hence the where they do not exist, or in habitats from level of carp control from such stockings which carp have been removed. Barriers in may be minimal. If, however, the existing the form of ‘fish screens’ have been used in adult population was severely reduced, for Tasmania to attempt to prevent the spread of example, to less than 10% (Thresher 1997), carp from Lake Sorell and Lake Crescent. The then a stocked population of predators success of these screens has not been deter- might have a high chance of suppressing the mined but carp have not spread to date (W. carp population over a long time scale. Fulton, Tasmanian Inland Fisheries Despite its apparent appeal, biomanipula- Commission, pers. comm. 1998). Screens may tion is a highly controversial area of ecology, prevent movement of larger fish but it is diffi- and should not be undertaken lightly with cult to prevent movement of eggs, larvae or unrealistic expectations of success. There is, juvenile fish. Screens were also used in Pilby however, scope for such manipulations to be Creek in South Australia and a wetland near evaluated on a small scale in enclosed waters Bairnsdale in Victoria (Section 8.6.1, Box 9) to to explore the problems likely to be encoun- prevent carp from re-entering habitats. Such tered and the likely impacts on carp popula- screens are not effective in times of flood. tions before wider application. Other forms of barriers, such as electric barriers, In contrast to the situation in lakes or bubble curtains and sonic barriers have been impoundments where fish populations are used in other countries to exclude fish from typically closed to immigration and emigra- structures such as industrial cooling water tion, fish in rivers are able to migrate exten- intakes, but their effectiveness against carp is sively. This makes the task of reducing carp unknown.

128 Bureau of Rural Sciences 7.3.8 Emer ging biological contr ol feeding behaviour of carp. The risks and ben- technologies efits of any such release would need to be assessed. Recent advances in molecular biology and biotechnology have provided opportunities ‘Extremely high infertility rates to attempt the development of new biological would need to be achieved for control agents. The new control agents could fertility control to have any useful be live, naturally disseminating immunocontraceptives or artificially enhanced pathogens effect on carp populations.’ which specifically kill or disable the target pest species (R. Seamark, Vertebrate The use of any reproductive control mecha- Biocontrol Centre, ACT, pers. comm. 1999). nism must be evaluated using information on the ecological processes determining the Immunocontraception distribution and dynamics of carp populations in Australia. Modelling of both the fish The Cooperative Research Centre for the populations and the epidemiological pro- Biological Control of Pest Animals is investi- cesses is required. The value of fertility con- gating the potential of immunocontraception trol for carp management depends on the to prevent population growth in feral pests effectiveness of the techniques developed (Tyndale-Biscoe 1994, 1995). The approach and the levels of control required (Hinds and involves the delivery of a gene which blocks Pech 1997). A critical issue in fertility control reproduction mechanisms (usually via a for carp is the huge number of eggs pro- species-specific reproductive protein) when duced, compared with the small number of the host is infected by a recombinant virus. young produced by most terrestrial verte- This approach is currently under develop- brate pests and the density-dependent mor- ment for mice, rabbits and foxes and is high tality of juveniles (Sections 3.4.2 and 3.4.3). risk in terms of achieving a practical out- Because the number of spawning fish need come that reduces the environmental and to be reduced greatly to reduce the number economic damage caused by these pests. of young carp subsequently recruiting to the Immunocontraception requires a multi-disci- population, the capacity exists for non- plinary team to focus on the problem at affected females to produce sufficient viable many levels: molecular biology, immunolo- eggs to maintain current population levels gy, virology, reproductive biology, field (Hinds and Pech 1997). Consequently, ecology and population dynamics. The aim extremely high infertility rates would need to is to produce a species-specific infertility be achieved for fertility control to have any agent that will have a significant effect on the useful effect on carp populations. pest species without any effects on non-target species (Hinds and Pech 1997). Molecular approaches The immunocontraception antigen would Recent advances in molecular biology offer a have to induce an effective immune response number of potential approaches for control- which affects fertility to a level that reduces ling carp. These include chromosomal the abundance of carp to desired levels. The manipulation, gender manipulation and the delivery system would need to be practical, introduction of inducible or programmed cost-effective, species specific and affect a fatality genes (Grewe 1997). These methods sufficiently large proportion of the target can briefly be summarised as: population to reduce impacts. A delivery system which could meet these requirements Ploidy/chromosomal manipulation — Used may include the release of a genetically mod- to induce sterility. ified organism. Primary reproductive pro- Controlling sex composition of populations cesses that may be targeted to impair fertility — Single sex populations have been include the development of the gametes and achieved by treating gametes prior to fertili- the functioning of the gonads. Delivery sation under laboratory conditions. mechanisms for the antigen include the use of baits that may be designed to match the

Managing the Impacts of Carp 129 Hormonal treatment — Treatment with the of stocking millions of genetically-modified male hormone testosterone can produce all carp, and the environmental impacts of male fish, including some which are chro- killing huge numbers of carp. If these chal- mosomally female but which function as fer- lenges can be overcome, then fatal gene tile males. technology appears to be a viable and perhaps long-term strategy for environmentally Transgenic manipulation — New genetic benign control of carp in Australia. material can be inserted deliberately into the target species for example, to change sex Mathematical models have been used to functioning. assess the potential of fatal genes or inducible sterility genes to control carp and Fatality Gene (FG) — It has been considered other species (Davis and Fulford 1999; Davis that this method has considerable advan- et al. 1999a). The results suggest that these tages over others as a long-term application methods may provide long-term control, but with 100% security if correctly implemented the rate of spread of these genes into feral (Grewe 1996). populations is likely to be slow. Two forms of ‘fatal’ genes have been suggested. Inducible Fatality Genes (IFG) Sterile ferals involve breeding carp with a genetic, fatal weakness to an otherwise benign ‘trigger’ This approach is being investigated by substance, such as dietary zinc. After breed- CSIRO based on recent developments in ing this gene into the carp population over molecular biology and population genetics. several generations, a trigger can be applied, The concept is based on being able to influ- for example in the form of zinc-laden pellets, ence population dynamics by introducing an which activates the gene and kills fish carry- inducible sterility gene that renders individu- ing the gene. Programmed fatality uses a als within a population sterile. Like inducible similar idea, but the fatal gene is triggered at fatality genes, this approach is futuristic and a specific life history stage, such as the onset contains many challenges before it might be of sexual maturity. able to be applied to wild populations, but these approaches represent a range of previ- Development of fatal genes involves several ously inconceivable options that may distinct steps (from Grewe 1997): become practical with further advances in • identify and select appropriate genetic biotechnology. material for transfer. This must include the fatality gene and a reporter gene 7.4 Methods for impact • incorporate this genetic material into the r eduction carp genome 7.4.1 Fishways • deliver the material at a population scale. This includes stocking carp with The term fishway refers to any device that the modified genome allows fish to negotiate a barrier that would otherwise block fish movement. Several • monitor the spread of IFG through natu- designs of fishways are currently in use in ral populations via the reporter gene Australia. On low barriers, such as weirs up to six metres high, fishways are usually pas- • activate the trigger to activate the fatality sive devices, relying only on the flow of gene once the gene has spread through water to allow fish to move upstream. Larger the population to a predetermined level. barriers such as major dams must usually provide active assistance for fish attempting to move upstream, by lifting or pumping fish Each of these steps presents its own techni- up over the wall. cal and logistical challenges, such as safety testing, the longevity of the gene, the impact

130 Bureau of Rural Sciences Rock-ramp fishways are less sophisticated designs that can be used on low weirs less than one metre high. They mimic natural stream riffles and consist of a 1:20 sloping rock ramp that has a series of rock ridges interspersed with pools (Figure 20). Each ridge has a number of slots through which the water drops to the next pool. Fish ascend through the slots, resting in the pools before attempting the next step up the ramp. The cost for a rock-ramp fishway varies depending on the availability of suitable rock. High dams, such as Hume Weir, are too high for the preceding fishway designs. Alternative methods exist, such as fish locks, fish elevators (Clay 1995) and fish pumps (Marsden et al. 1997). Although fish pumps have not been used in Australia, a fish eleva- tor has been installed on Yarrawonga Weir on the Murray River and is currently undergoing testing. Fish transport has also been conducted at the Yarrawonga site, removing fish from the entrance to the fishway, trans- porting them by truck and releasing them Trap-and-truck fishways allow carp to be removed and upstream of weir to avoid their being drawn native fish to be placed upstream of dams and weirs. into a power station inlet (C. Lay, NSW Source: A. Toovey, NSW Fisheries. Fisheries, pers. comm. 1999). The most common design of fishway for native fish on larger rivers in Australia is the ‘Fishways may reduce the vertical-slot fishway (Mallen-Cooper 1994; impacts of carp by allowing Mallen-Cooper et al. 1995) (Figure 20). This native species increased access design features a series of pools and weirs, to habitats where their numbers with a vertical rectangular orifice in each have declined.’ weir through which water passes down to the next level. It allows fish to ascend a barrier by negotiating a number of small increases Fishways may reduce the impacts of carp by in water level without needing to jump. allowing native species increased access to These fishways work on a range of slopes habitats where their numbers have declined. from 1:18 for adult and large juvenile fish, to Movement is an essential part of life for all 1:30 where there are large numbers of small native fish species, whether it be in the form juveniles. The cost of a vertical-slot fishway of daily feeding movements over relatively depends on the height of the weir and may short distances, or long distance breeding range from $250 000 to $750 000 (Mallen- migrations. Mallen-Cooper et al. (1995) Cooper and Harris 1990). reported large numbers of fish, including carp, moving through the vertical-slot fish- Denil fishways consist of a channel filled with way at Torrumbarry. Enhanced native fish closely spaced U-shaped baffles that angle populations may reduce the competitive upstream (Figure 20). The baffles create an advantage that carp have in many habitats, area of low velocity near the base through and provide increased predation pressure which fish ascend. This design can be used on (Section 3.5.2). steeper slopes than the vertical-slot fishway, with a gradient of 1:12 being ideal. It is there- Fishways also allow dispersal of carp to fore cheaper to build than a vertical-slot fish- colonise new habitats. However, the ability way. of carp to negotiate fishways can be turned

Managing the Impacts of Carp 131 V-notch for auxiliary water at high tailwater levels Trash rack

FLOW

Diffusing screen EXIT

Note: Fishway shown with only two gridmeshes in place

ENTRANCE Notch in weir-crest for attraction water

(a)

FLOW

Figur e 20: Diagram of (a) vertical slot, (b) Denil and (c) rock-ramp fishways.

(b)

132 Bureau of Rural Sciences Slope 1:20 Elevation

Transverse ridges to be built with large rocks, forming a series of pools and corrugations. Plan

Ridge rocks to be Flow-control rocks Slots .30 m wide larger than median size of rocks in overall structure

02 m

(c) to their disadvantage. By installing traps at The higher diversity in hydrologically vari- the top of fishways, carp reaching the top of able rivers means that fish communities are the fishway can be removed and destroyed more constant over time than in hydrologi- while native fish are returned to the water. cally stable rivers where changes in abun- This process can be automated by installing dance of a few species can cause relatively electronic fishway monitors that distinguish large variations in community composition between carp and native species. A suitable over time. Regulating river flows to provide monitoring and image analysis system is cur- water for agriculture and rural communities rently being developed (B. Owen, University reduces the natural variability in flow of Melbourne, Victoria, pers. comm. 1998), regimes. Variable flows create a diversity of but more development is required to pro- habitats that in turn are able to support a duce a working prototype. greater diversity of fish species than simpler habitats. By implementing environmental 7.4.2 Flow management flow regimes that restore elements of the timing, frequency and variability of natural flow Rivers in the Murray–Darling system with the events, the dominance of carp in fish com- most variable hydrological regimes have the munities is likely to be reduced (Gehrke most diverse fish communities, containing a 1997b; Harris 1997). Many regulated rivers more even balance of species than rivers with carry unnaturally high, stable flows during relatively stable flows (Gehrke et al. 1995). irrigation seasons which allow carp to enter

Managing the Impacts of Carp 133 floodplain nursery habitats to breed. By 7.5 Cost of contr ol increasing flow variability, carp access to floodplain nursery habitats can be restricted, Purely hypothetical costs of complete carp simultaneously reducing the impacts of carp removal in irrigation channels in the on these habitats and potentially reducing Murrumbidgee Irrigation Area (MIA) have survival of juvenile carp. River flow objec- been estimated for four alternative methods tives currently being implemented in New (Roberts and Ebner 1997). Applying the South Wales rivers (Environment Protection chemical acrolein during the irrigation sea- Authority 1997) with a partial goal of reduc- son would cost $13.8 million, assuming that ing carp numbers include: approval could be obtained to use acrolein • protecting water levels in natural river for this purpose. Carp removal using rotenone outside the irrigation season was pools and floodplain wetlands during estimated to cost $1.4 million. Estimated periods of no flow costs using boat electrofishing were at least $1.9 million during the irrigation season, or • protecting natural low-flows at least $0.2 million outside the irrigation season. A similar hypothetical analysis for carp • protecting or restoring a proportion of control in wetland habitats estimated water freshes (small to intermediate flows) and draw-down would be highly effective and high-flows cost $102 000 over ten years, whereas physical removal using nets would be less effec- • maintaining or restoring the natural tive and cost $75 000 over ten years (Roberts inundation patterns and distribution of and Ebner 1997). Of these removal methods, floodwaters supporting natural wetland only chemical poisoning would be likely to and floodplain ecosystems ensure complete removal of carp from a given area. These two assessments made • mimicking the natural frequency, dura- many assumptions because appropriate data tion and seasonal nature of drying were not available. This means that the actu- periods in naturally temporary streams al costs incurred in practice may differ widely from estimated costs, but the estimates • maintaining or mimicking natural flow provide a reasonable indication of the likely variability in all streams cost difference between methods. The areas involved in these analyses in the MIA were • maintaining the rates of rise and fall of relatively small so that the total costs would river heights within natural bounds be much higher if these methods were to be applied across all carp habitats in large river • maintaining groundwater within natural systems such as the Murray–Darling Basin, levels or the Hawkesbury–Nepean. Harris and Gehrke (1997) estimated the staff • minimising the impact of instream struc- costs for field sampling in the New South tures Wales Rivers Survey at $215 per staff member per day. This covered salary, on-costs and • minimising downstream water quality government travel allowances. This figure impacts of storage releases contains considerable savings obtained by using summer students and volunteers to • ensuring management of river flows reduce the time contribution of salaried staff. provides the necessary means to address The full cost in 1999 of a three-person elec- contingent environmental and water trofishing crew working to catch carp for a quality events. five-day working week was $5400. Vehicle lease and fuel costs may range between $500 and $800 per week. Full-sized electrofishing boats can cost between $40 000 and $90 000, although this cost can be spread over the

134 Bureau of Rural Sciences working life of the boat. Maintaining an electrofishing boat in safe working order is also a significant cost that could average $100 per week for the working life of the vessel. The NSW Rivers Survey caught approximately 50% of carp larger than 100 millimetres from a 0.24 hectare section of the Bogan River near Bourke in New South Wales by repeat- edly fishing over five days. The cost of electrofishing to reduce carp from other habitats can be estimated from this information and will be influenced by the amount of volunteer labour available, the need for qualified electrofishing crew, and whether a boat is purchased or leased.

‘Carp eradication attempted in Victoria cost over $1 million and was unsuccessful.’

Many of the high-technology methods described in Section 7.3 are currently being developed for other pest animal species. Although further development is needed to apply these techniques to carp, there could be considerable savings from the success of work already under way. Carp eradication was attempted in Victoria in 1962 by poisoning 1300 small dams. The exercise required 200 working days and $50 000 (Victorian Fisheries 1991a), equivalent to over $1 million at current values, and was unsuccessful. The cost of removing carp from small water bodies can be quite low, costing as little as a few thousand dollars for a single attempt. This expenditure may be justified in isolated habitats where recolonisation can be prevented. But the cost of effective control will escalate as the size of the habitat and the probability of reinvasion increase.

Managing the Impacts of Carp 135

8. Strategic management at the local and r egional level

Summary formance indicators then need to be defined which can be used to measure progress This Chapter outlines the process for plan- against the management objectives. ning and implementing strategic management of carp at local, regional and national The third step, implementation, is dependent levels. The four components of the strategic on an integrated approach for success. approach to carp management are: defin- Although much of the responsibility will rest ing the problem, developing a management with a range of government agencies, cooper- plan, implementing the plan, and monitor- ation and ownership must also be undertaken ing and evaluating results. with other stakeholders and community groups. Ownership of carp management must The first step in developing a management ultimately reside with many agencies and strategy is to define the problem. This means groups, not just those with fisheries interests. determining the nature and scope of the management concern (for example, loss of The fourth and key step is monitoring and water quality or aquatic vegetation). A evaluation. This should occur at different number of factors in addition to the pres- levels throughout implementation and on ence of carp can contribute to observed completion of actions. The efficiency of the problems, including human interference, operation needs to be monitored to ensure habitat type, local influences on water flow that the management plan is executed in the and quality and other fish species present. most cost effective manner. Monitoring will The problems caused by carp may affect help identify inefficiencies so the manage- many natural resources. Therefore the man- ment strategy can be continually refined. In agement of carp as a pest species is a natu- addition, the effectiveness of the program in ral resource management issue which achieving the objectives needs to be moni- extends well beyond the realm of traditional tored so that either the program objectives or fisheries management. the management strategy can be modified if necessary, in the light of further knowledge The second step is to develop a management and experience. This may mean modifying plan. This must include clear objectives set the objectives, if they are unrealistic, or in terms of the economic and/or conserva- adding new objectives. Effectiveness is deter- tion outcomes being sought. These manage- mined by evaluating achievements and out- ment objectives should include interim and comes against the performance indicators long-term goals. Developing the plan will included in the management plan. Different involve an assessment of the most appropri- techniques may have different success rates ate control technique(s) and strategy and under different circumstances. Economic setting the priorities for management. Best frameworks are needed to assist in the results in pest management are often assessment of the relative cost and value of achieved with a combination of techniques alternative strategies. Such frameworks rather than relying on a single technique. require: the definition of the economic prob- Options for carp management include: pre- lem, data on the relative costs of different vention of further spread, local, small-scale carp control strategies, and an understand- poisoning or removal, exclusion, habitat ing of why the actions of individual man- rehabilitation to enhance native fish species, agement agencies may not lead to optimal commercial or recreational removal, and levels of carp control and how management wide-scale control options which may may be improved. include new technologies. In developing a management plan, one or more of these This chapter includes three case studies: options need to be selected that will best meet ‘carp in a confined wetland area’, ‘rehabili- the management objectives. Measurable per- tation of a small stream’, and a ‘national approach to carp management’.

Managing the Impacts of Carp 137 8.1 Intr oduction appropriate strategic approach at national, regional and local levels. It describes the The preceding chapters have described cur- application of such processes in three case rent knowledge concerning carp (Cyprinus studies: one relating to the removal of carp carpio) in order to develop general princi- from wetlands, another concerning the reha- ples and strategies for best practice manage- bilitation of a small stream, and the third a ment of carp. The four components of the national approach to carp management. strategic management approach which can be applied to carp management have been previously outlined by Braysher (1993) 8.2 Define the pr oblem (Figure 1) and consist of: Chapters 3 and 5 set out the initial steps in • defining the problem (Section 8.2) defining the problems caused by carp. Chapter 4 outlines public concerns – which • developing a management plan (Section will assist in determining who the stakehold- 8.3) ers are that ‘own’ a carp problem. Chapter 7 details techniques for measuring impacts. • implementing the plan (Section 8.4) The impacts of carp on industry and the environment have not been fully evaluated • monitoring and evaluating progress and costings are not available (Chapter 5). (Section 8.5). This is an area in urgent need of research (Section 10.4). The main problems attributed The challenge for managers and other stake- to carp are declines in water quality, declines holders is to use the information in the pre- in aquatic plants and invertebrates, declines ceding chapters, together with the process in recreational fishing and more doubtfully, outlined in this chapter, to develop a strate- declines in native fish populations and gic management plan to address the damage stream bank erosion (Sections 5.2 and 5.3). caused by carp. Because the scientific evidence for these impacts is often not robust, it is important Much of the carp management undertaken that problems attributed to carp are clearly to date can be described as ‘crisis manage- defined at the start of a management pro- ment’ which has been undertaken with little gram, so that performance measures can be or no forward planning, when the problem put in place and fully evaluated to determine becomes to big too ignore. This type of if the program succeeds in reducing the unplanned management should be avoided problem (Sections 8.3.4 and 8.5). because it usually has little long-term effect and it is expensive to conduct recurring crisis Mapping plays an important role in defining management. It must be replaced by a more the problem and developing a management coordinated and strategic approach which plan. At the broadest scale (Figure 2) maps will be more effective in terms of both costs can be drafted to show the current and and achievements. potential range of carp to help inform plans to reduce the spread of carp at the national Strategic management can only be undertak- level. en following the formulation of careful plans after assessment of available options At a regional level, maps can assist in deter- (Section 8.3). Strategic management is mining priority areas for different levels of required where it is clear that carp damage carp management which may range from will require continuing management and local eradication to preventing spread to no involves integrating control options into management. The maps can divide regions/ water body and habitat management to catchments into different management units achieve specific reductions in damage. depending on their economic, recreational and conservation value. These maps can also This chapter explains how to use available highlight factors such as the density of carp information and processes to develop an and logistics such as access which will have

138 Bureau of Rural Sciences implications for the management option to determine if the management objectives chosen. The Carp Control Coordinating are met once the management strategy is Group (Section 6.2.2) has developed a guide implemented. to setting priorities for carp management. Maps can range from topographic maps or 8.3.1 Define objectives aerial photographs with overlays to interac- The objective of pest control is to reduce or tive computerised Geographic Information prevent the damage caused by the pest using Systems. A series of maps showing carp dis- the most cost-effective and safest methods tribution and abundance over time may indi- possible, while maintaining long-term man- cate changes associated with land, water and agement goals. The objectives should be carp management and provide a basis for defined in terms of outcomes which can be evaluating and modifying a management measured. That is, what will be achieved program. where and by when. ‘Mapping plays an important Examples of the types of objectives which role in defining the problem and may be set for carp management could developing a management plan.’ include: • increase diversity and density of wetland Carp impact (or impact potential), distribution plant areas and fish habitats in a defined and abundance should be mapped at scales area by 40% over the next three years relevant to the required size of management • limit the distribution of carp into new operations – irrespective of jurisdictional areas at the edge of their range boundaries such as catchment and local and State/Territory government boundaries. • improve water quality by reducing turbidity by 10 Nephelometric Turbidity 8.3 Develop a management plan Units (NTU) per year over the next two years in a defined area or river reach There are four components to a manage- • increase to a defined level the numbers ment plan: and/or distribution of native fish in a Define management objectives — Objectives defined catchment area or river reach are a statement of the planned achievements, defined in terms of desired outcomes • increase numbers of carp removed by — usually conservation or economic bene- 200% through commercial and recre- fits. Objectives state what will be achieved, ational fishing over the next two years in where and by when. a defined area or river reach

Select management options — The manage- • eradicate carp from defined areas, for ment option is selected that will most effec- example, irrigation channels (for eco- tively and efficiently meet the management nomic reasons) or areas with threatened objectives. The options include: precaution- native fish (for conservation reasons) by ary management, eradication, sustained a definite date management, targeted management, one-off management, and no management. • eradicate newly introduced carp from Develop management strategy — This defined areas by a defined date to pre- defines the actions that will be undertaken vent them entering a river system or — who will do what, when, how and where. spreading It describes how the selected management options will be integrated and implemented • eradicate newly introduced carp from a to achieve the management objectives. river to protect a population of threatened native fish species and their habitat Define performance indicators — This is a by a defined date. list of measurable factors which will be used

Managing the Impacts of Carp 139 The carp control objectives need to be achiev- carp numbers achieved with each control able and have outcomes that can be mea- treatment is likely to vary between different sured independently from the other factors habitats, and even between years because of (for example, other fish species) that may different climatic conditions. The size of the affect the indicators (for example, water tur- habitat covered by the control program, and bidity) in a disturbed catchment. The objec- the resources available to control carp, will tives of carp control need to be integrated also have a large influence on the number of with other management plans (for example, treatments required to achieve meaningful regional water plans) and national and control. regional strategies (for example, the National The objectives established may refer to pro- Strategy for the Conservation of Australia’s gressively increasing the number of habitats Biological Diversity (Commonwealth of that have been treated, such as wetlands, Australia 1996) and The Algal Management farm dams, irrigation channels or council Strategy (Murray–Darling Basin Ministerial ponds, and could include establishment of Council 1994)). strategies to prevent recolonisation by carp. Generally, objectives for carp populations should be set in terms of the desired density 8.3.2 Select management options of adult carp which is likely to achieve the desired reduction in impact. In some places, Management of carp falls into two main cate- such as wetland nursery habitats, the density gories: reactive and strategic. Reactive man- of juvenile carp may be more appropriate. In agement can also be categorised into: one- more complex scenarios, a combined mea- off, where a single control activity is con- sure of the number of juveniles in relation to ducted in response to a specific problem; the number of adult carp may give a clearer and continual, where control is conducted picture of the status of the carp population. on a continual basis, usually because no Objectives should not be limited to carp long-term strategy to reduce impact has been populations, but must include targets for the planned. Strategic management options are impacts of carp. These may include, but are usually better planned with more careful def- not limited to, public perceptions of carp inition of the problem and consideration of population trends, the amount of aquatic objectives and options. vegetation, water quality objectives or Once an objective is set, a management angling catches. option can be selected. In selecting a management option, it is important to match it to ‘Objectives should not be limited the desired objective and to be realistic in to carp populations, but must terms of the available resources and techni- include targets for the impacts cal feasibility. This is particularly important of carp.’ for carp, as many of the possible control options outlined in Chapter 7 are not currently available. The construction of a ‘deci- Objectives may include public perceptions sion matrix’ may be a useful aid for evaluat- of carp population trends if negative public ing which options are most appropriate perceptions of high carp numbers is seen to (Step 7 in Appendix A). be a problem in its own right. It may take many years to reduce impacts to acceptable The following seven strategic management levels. In these cases, it is necessary to set a options available for carp management have series of interim objectives which may been modified from Bomford and Tilzey include, but not be limited to, initial reduc- (1997). tions in carp numbers. Community groups and local government authorities may need to seek advice from government agencies on how to set performance objectives. The level of reduction in

140 Bureau of Rural Sciences Box 7: Risk management principles

The ‘precautionary principle’, agreed to by The National Strategy for the Conservation Australia under Principle 15 of the Rio of Australia’s Biological Diversity Declaration on Environment and (Commonwealth of Australia 1996) applies Development (Intergovernmental Agreement the precautionary principle and the follow- on the Environment 1992), provides two ing risk management principle: main ways to deal with uncertainty and risk ‘The causes of a significant reduction or involved with managing biological systems loss of biodiversity must be anticipated, to maintain biodiversity: attacked at source, or prevented.’ • When contemplating decisions that will Carp could contribute to such losses. affect the environment, the precautionary principle involves careful evaluation Prevention is better than cure. Protecting of management options to avoid, wher- ecosystems is far more cost effective than ever practicable, serious or irreversible attempting rehabilitation once the damage damage to the environment, and an is done. Some such changes can never be assessment of the risk associated with rectified. Emphasis must, therefore, be various options. given to preventing carp spreading into new areas. • When there are threats of serious or irreversible environmental damage, lack of full scientific certainty should not be used as a reason for postponing measures to prevent environmental degradation.

Precautionary management are suspected to occur and where there is a risk they might spread to higher value habi- Precautionary management can use the tats. Alternatively, precautionary manage- above principles to reduce risk to ecosys- ment may be directed at containing known tems. As carp have not yet spread across populations to prevent their spread. their potential range, an important management option is to prevent their spread. The Pathways by which carp can spread include: spread of carp throughout Australia is con- intentional release, accidental release, tinuing, dramatically illustrated by their release through ignorance, flooding, and recent introduction and establishment in transport of fish and eggs by wildlife. Tasmania (Section 6.3.5). Management options need to be developed to block each of these pathways to prevent ‘Preventing futher spread of further spread. The potential mechanisms of carp into new catchments and each pathway and potential management options are given in Table 14. regions of Australia must be an over-riding priority for carp Preventing further spread of carp into new management.’ catchments and regions of Australia must be an over-riding priority for carp management. Prevention of such an expansion in range is It is important that carp do not expand their both desirable and feasible through range into other areas of Australia where approaches which may include: they do not currently occur, particularly into areas of high commercial or conservation • Vigilance by the public, water authori- value. Precautionary management may ties and resource managers, as well as therefore be applied to habitats where carp strategic monitoring of fish populations

Managing the Impacts of Carp 141 Table 14: Key pathways which can allow expansion of the range of carp in Australia.

Pathway Potential mechanisms Proposed actions Intentional release Deliberate transfer to establish new popula- Legislation, education, tions for use as bait, to develop new angling monitoring and notification populations, or for ornamental value of new locations

Accidental release Use as bait in ignorance of the law, Education on the potential misidentification of carp for goldfish, contam- effects, correct identification, ination of fish stockings improved hatchery controls, education and quality control measures within hatcheries

Release through ignorance Use as bait in ignorance of the law, release Education on the potential of fish into storm water or sewage, misidenti- effects, correct identification fication of carp for goldfish

Flooding Natural movement into wetlands, or above Use of barriers barriers Transport by wildlife Carried by birds, foxes Nil

Transport of eggs Carried on the feet or feathers of birds Nil

in critical areas, to detect and eradicate ronment. This should use a variety of new outbreaks as soon as possible. methods (including signs, posters, web- site, telephone information line, media • The use of anglers and development of stories, paid advertisements, angler a ‘spot a carp’ campaign in critical areas press) and consider both accidental and would maximize public participation. As intentional spread. In particular, addi- was the case in Tasmania, it is likely that tional efforts should be targeted to invasions of carp into new areas will be groups who are more likely to cause first noticed by the general public. A spread such as coarse anglers and national phone hotline or internet site anglers who may wish to use carp as (for example www.sunfish.org.au/recfish/ bait. NCTF/Carpdatabase.htm) may be a useful reporting mechanism. This could also be • Legislation and regulations need to be used to provide public information. A consistent and penalties may need to be rapid management response depends reviewed to highlight the importance of on new outbreaks being immediately the issue. Compliance staff, particularly reported to relevant agencies and these outside the existing range of carp, need agencies having the necessary resources to be informed of the importance of this and expertise to implement pre-planned issue. strategic actions. • Existing barriers may be assisting the • A national, coordinated community edu- spread of carp. Fishways may be operat- cation program to emphasise the impor- ed in ways to favour native fish move- tance of this issue and risks to the envi- ments but not carp (for example, by

142 Bureau of Rural Sciences modifying attraction flows). In some 2. Immigration rate is zero — If animals can instances, the erection of barriers may migrate into the eradication area, eradica- be an option to prevent further spread, tion will be unachievable or transient. although native fish movements need to Eradication of carp can most easily be met be considered. in isolated water bodies. Further introductions can occur, however, through a range National Eradication of means such as floods, anglers or birds. Barriers such as screens across rivers or Eradication is the complete removal of all lake entrances may prevent migration of carp from a defined area by a time-limited adult carp, but are unlikely to be success- campaign. National eradication has not been ful for small juvenile fish that can pass achieved for any widespread vertebrate pest through spaces in the screen. species on mainland Australia (Bomford and O’Brien 1995). Despite numerous large-scale 3. All carp must be at risk — Removal tech- attempts, no eradication campaign against niques need not take all animals in the any well established, introduced vertebrate one attempt, but all reproductively and pest has been successful on any continent potentially reproductive members of the (Caughley 1977; Macdonald et al. 1989; population, that is, adults, juveniles and Usher 1989; Bomford and O’Brien 1995). eggs, must ultimately be removed for Eradication of carp from Australia is not pos- eradication to be achievable. sible at present. This option should be maintained as a longer term goal which might be 4. Populations can be monitored at all den- achieved if new technologies become avail- sities — If animals cannot be detected at able, although biotechnological techniques low densities, there is no way to measure are more likely to assist managers to reduce the success of the eradication program. As carp numbers and maintain them at lower densities rather than enable them to attain carp inhabit a wide range of (often turbid) national carp eradication. aquatic habitats they are not easily observed or caught at low densities.

Local eradication 5. Discounted cost–benefit analysis favours Successful local eradication of small pest eradication over control — There are few populations has occurred, including for carp quantitative measurements for agricultural (Section 6.3). Before eradication is attempted or environmental damage caused by terres- all six of the criteria outlined by Bomford trial pests, making cost–benefit analysis dif- and O’Brien (1995) should be met: ficult. There are no such data for carp. Eradication usually requires a large initial 1. Rate of removal exceeds the rate of increase outlay, but if successful, there are no further at all population densities — If the removal costs and benefits accumulate indefinitely. rate is less than the rate of replacement at any Even if eradication would be more cost population density, then eradication cannot effective than sustained control, the bene- be achieved. Populations subjected to con- fits should still be weighed against the alter- trol usually compensate with higher survival natives. Sustained control may be more cost rates because of increased availability of effective than a one-off successful eradica- resources (Caughley 1977, 1985; Caughley tion. The chance of the failure of an eradi- and Krebs 1983). As density declines, it pro- cation attempt and the cost of potential gressively becomes more difficult and expen- reintroduction also need to be taken into sive to locate and remove individuals. Hence account. removal rates tend to decline at low population levels and if the removal rate declines to 6. Suitable socio–political environment — less than the rate of population increase, then Even when technical and economic crite- populations will not decline further. ria can be met, social and political factors can play an overriding role in determining

Managing the Impacts of Carp 143 the prospects of successful eradication. increasing and being encouraged by some Strong support from the wider community government agencies (Section 6.3). is needed before eradication should be Commercial harvesting is likely to be eco- attempted. In particular there would need nomically viable only in restricted areas. The to be support for the cost of the program sustainability of the industry has not been and the control techniques used (for assessed and further markets, products and example, there may be considerable resis- export opportunities need to be explored tance to the use of poisons or introduction (Section 5.4). As outlined in Section 7.3.1, of viruses). Eradication may also be commercial harvesting is likely to have little opposed by industries based around the impact on carp populations in the long term use of the pest involved and this must be but may reduce local populations to minimise damage as a short-term strategy. considered in the encouragement of com- Consideration needs to be given to the mercial carp harvesting. impact a more effective control measure would have on an established carp harvest- ‘The potential reintroduction of ing industry, for example, the impact of a carp into waters from which carp biological control agent should one be they have been eradicated developed. ‘Sunset clauses’ should be part of remains a problem which is any government assistance towards developing commercial fisheries as a short-term con- difficult to address.’ trol measure, giving notification that the fishery will end if more effective carp control An affirmative response to all of these crite- techniques are successfully developed. ria is required before eradication should be attempted. A negative against any of the first Targeted management three criteria will make eradication unachievable, and a negative against any of Targeted management is used when the con- the last three criteria will make eradication trol effort is targeted to manage carp damage impractical. Applying these six criteria to at a particular time, possibly when the popu- carp shows that national eradication is not lation is most susceptible to control. The key currently possible nor likely to be in the to this strategy is to monitor the population forseeable future. Eradication of carp may be to enable actions to be undertaken at the achievable in smaller, isolated waterbodies, most appropriate time. An example of this such as farm dams, but not in most river sys- may be poisoning a lake during low water tems. The potential reintroduction of carp levels (see Sanger and Koehn 1997) or into waters from which they have been erad- before the spawning season. icated remains a problem which is difficult to address. One-off management One-off management involves a single action Sustained management to achieve a long-term or permanent reduc- Sustained management involves an initial tion of carp damage to an acceptable level. An widespread campaign to reduce populations example of this may be the release of an effec- to low levels, followed by maintenance control tive biological control agent, if one becomes to prevent population recovery. Before adopt- available for carp, or building an exclusion ing this approach, resources must be allocated barrier. Future biotechnologies may enable to ensure that control is maintained into the managers to achieve and maintain higher lev- future. An example of this may include an ini- els of carp control at lower costs. The unavail- tial large-scale harvesting operation followed ability of biocontrol options is currently a by regular, continued harvesting. major impediment to widespread reduction of carp numbers in Australia. Commercial carp harvesting is being undertaken only on a relatively small scale in Australia (Section 5.4), but is currently

144 Bureau of Rural Sciences No management The management strategy defines the actions that will be undertaken to achieve the man- In some situations, the costs of control agement objectives. It sets out the tech- exceed the benefits and no carp control may niques to be used and when, where and how be the most cost-effective option. In some they will be used. Control techniques need smaller, isolated waterbodies of no signifi- to be compared for effectiveness, cost-effi- cant commercial or conservation value, there ciency, safety, and acceptability. A combina- may be little value gained from carp control tion of control techniques may be needed to actions. No management has largely been achieve optimal effectiveness. Management the management option undertaken for carp strategies at the national level must also to date, allowing carp to increase in both include options to develop new control tech- range and abundance as a pest species niques. (Chapters 2 and 6). Adaptive experimental management 8.3.3 Develop a management strategy Strategic management is based on the concept of adaptive management, in which the Having determined the most appropriate management plan is flexible, responding to strategic management option from the seven measured changes in economic, environ- alternatives listed in Section 8.3.2, the next mental and pest circumstances (Walters step is to integrate the chosen management 1986). In passive-adaptive management techniques from Section 7.3 into a manage- (Walters and Holling 1990) a single strategy ment strategy. is selected, implemented, monitored and This section covers some of the issues that evaluated, and adapted according to the suc- need to be taken into account in developing cess or otherwise of the strategy. The active- a management strategy, including: adaptive approach puts up a number of alternative strategies which are all imple- • value of adaptive experimental mented, monitored and evaluated, and management adapted according to which strategy is best (Walters and Holling 1990). The latter tech- • experimental design nique is more experimental and requires standardisation of monitoring and effort • availability of resources to adequately across strategies, replication of strategies implement the options and, ideally, nil-treatment areas where no control strategy is imposed. The challenge • priority setting for those responsible for carp management is to use the information in the preceding • environmental, social and legal accept- chapters and the processes described in this ability of the management strategy and chapter to develop a strategic management actions plan to address the damage caused by carp.

• decision analysis framework Experimental design (Adapted from Olsen 1998 and Underwood 1990) • size and location of the management unit including water type and local con- Well designed experiments are often the ditions only way to increase our knowledge of a pest species and to evaluate the effectiveness • contexts of local, regional and national of management techniques. Good experimental design will help ensure that results approaches. are sufficiently conclusive to make recommendations for further management. At the simplest level, management actions should involve some degree of monitoring

Managing the Impacts of Carp 145 and evaluation so that management can be design which will also allow the effectiveness of progressively improved over time (in accor- different control options to be tested. dance with Figure 1). If the resources allow, Ideally, the null hypothesis should be tested and the situation is appropriate, more informa- with a concurrent comparison of similar tion can be obtained by comparing different habitats with different carp densities. management strategies or a single manage- However it is clearly difficult to achieve a ment strategy against a non-treatment ‘con- range of carp densities within a connected trol’. water body, short of netting off large sec- Well designed experiments must follow a tions of habitat (although some experiments logical procedure such as that outlined in the have used carp exclusion cages to monitor steps given in the following two examples: the recovery of macrophytes). Because a range of carp densities are not always possi- Example 1 — the possible ef fect of carp ble to achieve at comparable sites, studies on macr ophytes (Section 8.6.1; Pilby Creek, Box 9) may sim- Step 1 — Observation: Observing a pattern ply monitor changes at a single site following or departure from a natural pattern — for manipulation of carp numbers. example, different biomass of macrophytes The most conclusive results will be obtained associated with different biomass of carp. by direct comparisons between similar sites Step 2 — Theory: A theory arising from the where the only differences are the control above — and one which is often tested options, resultant carp numbers and the (Section 5.3) — is that low macrophyte responses of assumed links such as post- biomass is associated with high carp biomass. management macrophyte biomass. If there Note that this makes no judgement about the are inherent differences between manage- reasons for this or causal links; it is simply a ment sites such as different riparian vegeta- theory based on observed or predicted (for tion, water flow and quality, sediment com- example, based on diet studies) patterns. If the position, composition of flora and fauna and pattern is proven, further testing would be pre-management macrophyte biomass, the required to determine why high levels of carp results will be confounded and a direct com- are associated with low levels of macrophytes parison of results is not valid. (see Step 6). Important elements of experimental design Step 3 — Hypothesis: During the building include: use of non-treatment ‘controls’; of a hypothesis, specific predictions are replication of treatments and non-treatment made from competing theories. Most controls across a number of sites; random hypotheses are constructed in the positive allocation of treatments and non-treatment form that makes a prediction that there will controls to sites; standardised data collection be a difference between treatments. For across sites and over time; methods to avoid, example, ‘Where carp biomass is high, there overcome or account for confounding will be a reduced biomass of macrophytes’. effects; and the use of appropriate statistical analysis to increase the power of the conclu- Before the Step 4 — Null hypothesis: sions and avoid the incorrect acceptance or hypothesis can be tested statistically, it is rejection of null hypotheses. usually restated in the negative form, called a null hypothesis, which usually states that Step 6 — Support or r eject the null there will be no difference between treat- hypothesis: The hypothesis is either upheld ments. For example, ‘There will be no differ- or rejected depending on whether the null ence in the biomass of macrophytes at differ- hypothesis is supported by the analysis of the ent carp biomass.’ data collected. The next step is to refine the original theory to establish more direct causal The above null Step 5 — T est or experiment: links between management options, carp hypothesis could be tested by comparing macro- numbers and resultant impact. Theories that phyte communities in similar bodies of water with could explain the lack of macrophytes at high different carp densities. Alternatively, carp num- carp levels are that ‘carp at high densities bers could be manipulated within an experimental

146 Bureau of Rural Sciences graze and uproot macrophytes faster than Step 5 — Experiment: This is a 3-factor they can recover’ and/or ‘high densities of experiment: carp (C), stock access (S), no carp suck up large amounts of sediments riparian vegetation (V) — alone or in combi- resulting in siltation of aquatic vegetation and nation are hypothesised to cause stream increased water turbidity which reduces light bank slumping. A factorial experimental penetration required for photosynthesis’. The design to test these factors in combination is second theory is more complex than the first required to determine whether there are any because there are a number of assumed interactions between them. Hence stream causal links and a number of experiments bank slumping is assessed under the follow- would have to be conducted to determine ing combinations of treatments: whether carp are the main cause of siltation • carp densities high (+C), stock access and turbidity, and whether these factors are the main reason for macrophyte decline. (+S), no riparian vegetation (+V) which is the treatment combination which has Example 2 — the possible ef fect of carp, all factors set to cause slumping livestock access and bank vegetation on str eam bank slumping. • carp densities high (+C), stock access Step 1 — Observation: Observing a pattern (+S), riparian vegetation intact (-V) or departure from a natural pattern — for example, undercutting and slumping were • carp densities high (+C), no stock access observed to occur in streams where carp (-S), no riparian vegetation (+V) were present. Other factors that were also associated with bank slumping were clearing • carp densities high (+C), no stock access of bankside vegetation and stock access. (-S), riparian vegetation intact (-V) Stream bank slumping Step 2 — Theory: • carp densities low (-C), stock access may be caused by carp, stock access and/or (+S), no riparian vegetation (+V) clearing of bankside vegetation. Step 3 — Hypothesis: During the building • carp densities low (-C), stock access of a hypothesis, specific predictions are (+S), riparian vegetation intact (-V) made from competing theories. Most hypotheses are constructed in the positive • carp densities low (-C), no stock access form that makes a prediction that there will (-S), no riparian vegetation (+V) be a difference between treatments. For example, if carp are controlled, stock are • carp densities low (-C), no stock access excluded and/or vegetation on banks is (-S), riparian vegetation intact (-V) intact stream bed slumping will not occur, which is the treatment combination but it will occur if carp are not controlled, where all potential slumping factors are stock have access or if there is no riparian absent. vegetation.

Step 4 — Null hypothesis: Before the Each of these treatment combinations would hypothesis can be tested statistically, it is need to be replicated at more than one site usually restated in the negative form, called a so that the results obtained could be null hypothesis, which usually states that analysed statistically. there will be no difference between treatments. For example, ‘carp control, stock Step 6 — Support or r eject the null access and/or stream bank vegetation will hypothesis: The results would enable the not affect stream bank slumping’. null hypothesis to be accepted or rejected for each of the three factors tested alone and in combination.

Managing the Impacts of Carp 147 Box 8: Economic Frameworks

Economic frameworks require: The effort applied to protect an agricultural or conservation resource will be influ- • a definition of the economic problem enced strongly by that resource’s value and the discount rate applying to benefits • data on the relative costs and benefits that accrue from it. These factors influence of different management options vertebrate pest management (see Pearce et al. 1989; Ecologically Sustainable • an understanding of why some indi- Development Working Groups 1991; vidual actions may not lead to optimal Johnston 1991 for more detail). levels of control Discount rates • an assessment of ways in which government actions might intervene to Discount rate refers to the fact that people overcome market failure. usually prefer to receive benefits as early as possible and to pay costs as late as possible. The weighting of present over future Managers can use economic frameworks is known as discounting, and the rate at to select the most appropriate manage- which the weight changes is the discount ment strategy for their circumstances. This rate (Pearce et al. 1989). Calculating dis- can be done using the stepwise approach count rates involves using the reverse outlined in Appendix A. Ideally, managers equation to that used for calculating inter- could use this approach to optimise con- est rates on invested money. trol effort, but often budgets are con- strained by competing demands and less There is concern about the environmental than optimal amounts are available. implications of applying the market dis- Managers have to allocate priorities to count rate to production systems (Pearce areas where control will be conducted. et al. 1989; Ecologically Sustainable Priorities will depend on the goal of con- Development Working Groups 1991). The trol, the method to be used and the relative rate may be higher than society wants in threat and manageability of carp in the order to protect desired benefits, such as area. Complete information is almost protecting water resources and/or natural always absent to support many of the deci- biodiversity. Governments may intervene sions needed for this process and man- to redress the balance between the objec- agers will often have to make ‘best guess’ tives of the private landholder or water estimates. This process will, however, give users and those of society, although this defensible decisions, especially if they are may not always achieve the desired result empirically tested by monitoring and eval- (Ecologically Sustainable Development uating the outcomes. Managers also need Working Groups 1991). Often, sufficient to estimate losses and potential future loss- knowledge of the true costs and benefits is es from environmental degradation caused not available, or the benefit may not be by carp. easily valued. The Ecologically Sustainable Development Working Groups (1991) report on sustainable agriculture urges caution on government intervention in this area.

148 Bureau of Rural Sciences Valuing benefits Benefits that are normally subject to mar- Animal welfare organisations would also ket forces, such as changes in productivity like the suffering caused by harvesting or of a commercial fishery, are relatively easy control techniques to be factored in as a to value in monetary terms, although as potential cost to the Australian community mentioned earlier, the impact of pests and in vertebrate pest management decisions the costs and benefits of control have usu- (Appendix A; Choquenot et al. 1996). As ally been poorly quantified. Some benefits, yet, this has not occurred for any pest however, are not normally marketed and species in Australia. hence are not readily assigned a monetary Economic frameworks of the type outlined value. Examples include animal welfare in Appendix A also need to identify the dif- and protecting native plants and animals, ferent economic options and roles for biological communities or landscapes. In national agencies, regional managers such the case of carp, changes to water quality, as the Murray–Darling Basin Commission, aquatic habitats or native endangered fish State agencies, catchment authorities, local populations have not readily been Shires and associations. In some cases assigned a monetary value. Conservation there may be a need for the smaller, local values such as intact wetlands or native authorities to be supported by larger, fish populations have yet to be reliably national groups. Such frameworks need to priced. Where carp control is being con- take into account both local and national sidered, however, such values should be considerations. included in the cost–benefit analysis. There is also a need for managers to esti- There is considerable debate on how to mate losses caused to other areas and value these non-market resources or industries should the ‘do nothing’ option whether they should be valued other than be exercised. At the same time, the oppor- in terms of their intrinsic value (Chisholm tunity cost of controlling carp versus and Dumsday 1985). Some economists investing in improvements in other indus- believe that useful techniques for valuing tries and alternative approaches to protect non-market resources will soon be avail- the environment need to be considered. able to assist decision makers. Current examples of these techniques include trav- Economic frameworks also need to con- el cost analysis (Pearce et al. 1989), sider the benefits of carp which may Hedonic Pricing (Streeting 1990) and increase with increasing variety, quantity Contingent Valuation (Wilks 1990). They and value of carp products. are based mainly on the concept of ascer- taining what individuals are willing to pay to protect or improve the environment (Pearce et al. 1989). There is no assurance that all natural resources can be valued accurately before they are extinguished or irreversibly damaged (Pearce et al. 1989). Developments in valuation techniques should be watched closely. In the mean- time, funding agencies and researchers should ensure, where practicable, that studies of vertebrate pest damage quantify the damage of pests on ecological sustainability of production and other systems, so that decision makers can take all likely consequences into account.

Managing the Impacts of Carp 149 Availability of resources to niques it is not sufficient to consider only adequately implement the options whether they work and how much they cost. Environmental, social and legal implications Economic frameworks can assist managers also need to be considered as do indigenous to assess the relative value of alternative con- cultures and animal welfare issues (Sections trol strategies for a pest problem and the rel- 4.5 and 4.6). Environmental effects, including ative benefits compared with other risks that impacts on non-target species, are important must be managed. particularly when commercial harvesting, poisoning or biological control options are con- Priority setting templated (Section 4.4). Opposition has been expressed toward many available or potential A structured approach to setting priorities is control techniques (Sections 4.3, 4.4 and 4.6), essential to ensure that resources are well for example: spent. A method for assigning priorities to areas for carp management is currently being • a large-scale commercial carp harvesting undertaken by the Carp Control industry, which may be seen as a substi- Coordinating Group (CCCG) (M. Braysher, tute for more effective but costly man- Carp Control Coordinating Group, unpub- agement options, has the potential to be lished data, 2000). Important steps to achiev- difficult to dismantle should more effec- ing this include: tive control techniques be developed 1. Dividing Australia into areas with and • concern about the impacts of commer- without carp. cial harvesting on non-target species 2. Assessing the difficulty and expense of • concern about the impacts of poisons on management for each area. non-target species 3. Identifying management areas where • the release of viral or genetically manip- eradication is possible. ulated organisms is not viewed favourably by the general public and it 4. Separating other areas according to other is likely to be difficult to convince oppo- major goals. nents of the safety of effective organisms because of perceived risks to public 5. Ranking each management unit based on health and non-target species. the threat from carp.

6. Determining the overall ranking which is reassessed after consideration is given to Decision analysis other secondary factors. Norton (1988) describes a series of questions that managers can ask to determine if pro- High priority should be given to identifying posed control measures are feasible and areas where carp do not yet occur and to acceptable. Similar questions and answers developing and implementing management are given for two carp control techniques in actions to prevent their introduction. Table 15. Ranking management units involves an These questions and answers have identified assessment of the importance of such issues several problems, including the: as biodiversity, water quality, cultural, tourism, and recreational values. • absence of biological control options that have been demonstrated to be safe Environmental, social and legal and effective for reducing the damage issues caused by carp When selecting appropriate control tech- • inability of harvesting to effectively reduce numbers in all areas

150 Bureau of Rural Sciences Table 15: Decision analysis table for considering factors affecting the acceptability of control measures for managing carp populations (questions after Norton 1988).

Questions Answers

Is the control measure: Harvesting Biological control*

Technically possible? Yes, in some areas Not at present** Practically feasible? Yes, in some areas Needs to be developed and tested Biologically effective***? Usually no Possibly

Economically favourable? Not cost-effective below a certain popu- Yes lation density. Not at all in some areas Environmentally acceptable? Mostly, with safeguards Yes, if target-specific

Politically acceptable? Yes ? Socially acceptable Yes ?

* Biological control is any control technique which involves the release of live organisms, such as: viruses or bacteria to causes diseases, live vectors to spread immunocontraceptives or genetically modified carp with ‘fatality’ genes ** Predator stockings possible but not tested. Most other options are not developed at present *** That is, the proposed control measure will reduce population size sufficiently to reduce damage levels

• problem of cost-effective harvesting include: discrete water bodies such as dams, billabongs on a floodplain which have the • uncertainty of future political and social ability to connect during high flows, and acceptability of biological control river reaches between barriers which pre- agents, especially the use of viruses and vent reinvasion. genetically modified organisms. Management units can also be based on socio-political boundaries, such as the boundaries of catchment management Management units groups, regional authorities (for example, jurisdiction of a water management agency) Management units for carp control can be or individual States, whose agencies may be defined at any scale — national, State, responsible for many management actions. regional or local. Given the mobility of carp Management at the boundaries of these units and their ability to move throughout river should be coordinated to achieve meaning- systems, together with their propensity to be ful outcomes on an ecological scale. spread by other means (Section 2.1), reinvasion can occur quickly. Managers need to recognise that different plans will be imple- 8.3.4 Define per for mance mented at different scales. Ecologically indicators based management units need to be of suffi- A final component of any management plan cient size to be effective and avoid reinva- is setting a series of performance indicators. sion but not so large as to be unmanageable Performance indicators should be developed and fail to function as a unit. The size of the so that they reflect the objectives of the man- management unit is likely to be determined agement strategy, are achievable and mea- by the size and type of the water body pre- surable. For example, an objective may be to sent. Examples of management units

Managing the Impacts of Carp 151 increase the amount of aquatic vegetation in addressed, and fosters a strong sense of a wetland by 20% per year by removing carp ownership of the management plan and and to prevent subsequent immigration by management which addresses the concerns installing barriers. Two performance indica- of all stakeholders. tors are needed here to measure the: • amount of aquatic vegetation each year 8.5 Monitoring and evaluation

• number of carp inside the barriers. As described in Section 8.3.1, the key to the success of strategic management is the moni- Performance indicators demonstrate toring of clearly defined performance indica- whether management objectives have been tors and evaluating the results so that the achieved. If success has not been achieved it efficiency and effectiveness of the program may be necessary to change or modify the can be assessed. Evaluation of monitoring management strategy. Variability in environ- data enables refinement of the control strate- mental conditions influences fish popula- gy in relation to the objectives. Without mon- tions and other ecosystem components and itoring and evaluation, a lot of money may must be taken into consideration when set- be wasted on ineffective campaigns. ting and measuring performance indicators. Therefore monitoring and evaluation is an essential component of best practice to The primary aim of carp management should ensure that carp control is efficient, effective be to reduce to acceptable levels the damage and safe. It is important to distinguish they cause. Therefore the effectiveness of between efficiency (relating to operational management actions can be measured objectives) and effectiveness (relating to per- against environmental variables such as den- formance objectives) as management can be sity of aquatic plants or a measure of water efficient but not effective. For example, 75% quality. of carp may be removed efficiently, and for Performance indicators should: little cost, but this strategy would be considered ineffective if the objective was to pro- • use standardised measurement indices tect aquatic plants and: a) carp removal was and procedures not continued or other control measures were not undertaken to prevent subsequent • use methods which can be undertaken population increases, or b) this level of pop- within the budget and skills available ulation reduction was insufficient to reduce damage to aquatic plants. • be monitored and evaluated on an Evaluation needs to: appropriate scale (Section 8.5). • compare the results from different management actions and different sites

8.4 Implementation • assess changes to performance measures over time, including the longer Implementation of carp management is term. described in detail in Chapter 9. As most waters are controlled or managed by government rather than private agencies, management strategies must be undertaken by these 8.5.1 Operational monitoring agencies in conjunction with public bodies Operational monitoring aims to assess the and community groups. The value of the efficiency of the operation in relation to what group approach to pest management is that was undertaken, where and for what cost, it fosters wider ownership of the problem. with the aim of improving efficiency. This The group approach requires local commu- may be in the form of a description of opera- nity support based on an understanding of tions and reporting the numbers or weight of the damage carp cause and how it can be carp removed or killed per unit effort. This

152 Bureau of Rural Sciences information can usually be collected by the don a program if the desired objectives are on-ground operators such as the organisers not being achieved. For this reason it is cru- of fishing competitions, or from commercial cial that monitoring programs are well harvesting records. planned and executed. Monitoring programs should, where possible, be designed to: Monitoring carp populations (Sections 7.1) and the impacts of carp is an essential, inte- • use indices of impact and abundance gral and continuing part of a carp control that are standardised to enable compar- program. The minimum monitoring neces- isons over time and among different sary includes: habitat types • monitoring carp density before a control operation • monitor impacts of the management program on valued resources, such as • monitoring again soon after the control fish habitats, aquatic vegetation or native operation fish species, as well as on carp abundance • periodic monitoring. • monitor before and soon after control operations, and then periodically ‘Monitoring should begin before the management program is • use methods that are easy and rapid. A implemented.’ better assessment is given by many approximate assessments over many The frequency of monitoring should be sites than by a few precise assessments determined by the way carp population data over relatively few sites will be analysed. Powerful population modelling techniques have been developed in • record information in a standardised for- fisheries science for the purpose of analysing mat that allows changes in indices of and predicting trends in fish populations impact and abundance to be compared over time (Hilborn and Walters 1992). These over time. Most State and Territory fish- models should be used wherever possible to eries agencies can provide suitable maximise the ability of monitoring to detect forms for recording this information long-term changes in carp populations. Different types of models have different data • assess carp abundance using indices that requirements, making it imperative that the are long-lasting, such as catch-per-unit- monitoring program collects the right data at effort, catches obtained over a relatively the appropriate frequency. Repeat monitor- large number of sites, or changes in the ing should at least be done in late summer to observed distribution of carp. Catches of increase the chance of detecting whether carp obtained from a single site are like- spawning has been successful. In isolated ly to vary greatly over time habitats where complete eradication has been successful, ongoing monitoring is not • ensure that sampling is not biased by, required unless there is a risk of reintroduc- for example, only sampling near bridge tion. crossings or boat ramps where access is Monitoring should begin before the manage- easy. Reliable sampling must be repre- ment program is implemented. It is part of sentative of all the carp habitats within assessing the problem and is an integral part the area of the control program of planning a management program. The outcomes of monitoring provide the basis for • make use of advice from professional many decisions on expenditure of effort and freshwater ecologists and fish biologists. resources. Monitoring is also used to evaluate and if necessary adjust, redirect or aban-

Managing the Impacts of Carp 153 In contrast to other vertebrate pests, such as cies can then integrate this information with foxes and rabbits, where the impacts are biological surveys, commercial fishery statis- often direct and observable, the impacts of tics, results of angling competitions, fish kills carp are more likely to be indirect and not and compliance reports. These assessments readily observable, requiring detailed analy- can then be coordinated among State agen- sis to detect whether any impact has actually cies by a central agency or committee at a occurred (Chapters 3, 4, 5), or whether the national level. management program has been successful in If monitoring data is held in a centralised reducing the level of impact. database and is accessible to other users, the analytical tools and models needed to assess ‘Interest groups can assist monitoring results in a consistent way can be coordinating agencies in record- made available to all groups involved in carp ing information on carp management. The advantages of a cen- distributions and density esti- tralised system include all carp control mates in a standard form.’ groups having access to the results of other groups to compare results, while the central agency retains the ability to see which man- Assessment of impact may be laborious and agement approaches are the most successful time consuming unless simple measures can or least effective. be used. The current state of knowledge on carp impacts is such that there are no widely In almost every instance, past assessments of applicable simple measures of impact. Part carp have provided indications of impact or of the monitoring program should therefore abundance, rather than exact measures. For include developing suitable measures for this reason the importance of standardisation each situation, in consultation with experi- must be emphasised. Standardisation of enced biologists and statisticians who are assessments of carp abundance depends on often employed by State fisheries agencies, the use of robust indices that reflect long- to allow for greater standardisation and coor- term trends in carp numbers. dination at a later time. Long-term information on carp impacts and 8.5.2 Per for mance monitoring and abundance is essential for management pro- evaluation grams because carp numbers can fluctuate Performance monitoring aims to assess the widely from year to year. Problems caused effectiveness of a management plan in meet- by variation in carp numbers can only be ing its objectives (Section 8.3.1) by taking overcome with long-term monitoring. measurements of the defined performance Ideally, carp monitoring should be tied in indicators (Section 8.3.4) and evaluating with existing monitoring frameworks for these results. The carp management program water quality and other aquatic ecosystem is evaluated by comparing information indicators to avoid duplication and allow acquired in the monitoring program against correlations to be drawn between habitat the pre-determined objectives. changes and carp density and population structure. Monitoring habitat quality of carp- ‘Carp control programs may free areas is also essential to allow a more quantitative assessment of the impact of carp take many years to achieve their where they become established in new full benefits.’ areas. Catchment Management Committees, River Management Trusts, River Some performance measures can be taken Management Committees and regional inter- by on-ground managers but others involve est groups can assist coordinating agencies complex ecological relationships and are in establishing and maintaining long-term better obtained by researchers. Performance monitoring programs, and in recording infor- monitoring usually requires a long-term per- mation on carp distributions and density esti- spective and some experimental and scientif- mates in a standard form. State fishery agen- ic rigour if results are able to be interpreted

154 Bureau of Rural Sciences accurately (Sections 7.2 and 8.5.2). In some To avoid the pitfalls of misinterpreting moni- cases, models can be used to predict results toring information, community groups and which can then be used to evaluate results local government authorities are advised to actually achieved. Both the model develop- seek advice from specialists in government ment and management actions can be con- agencies on how to design, conduct and tinually improved as more data are collected. evaluate performance monitoring programs. Carp population models and similar models The level of reduction in carp numbers of carp impacts have potential to be invalu- achieved with each control treatment is likely able in interpreting monitoring results to to vary between different habitats and judge whether targets are being met and in between years because of different climatic deciding whether further monitoring is conditions. Also carp control programs may required. take many years to achieve their full benefits. Experience and caution are needed in inter- One crucial outcome from evaluation is an preting short-term monitoring. Some impacts assessment of cost effectiveness of different of carp may not respond to carp removal management options. Many groups involved immediately, or may require specific flow in carp control will not have the resources to events such as floods or droughts to ‘reset’ test different methods. However, the cost the system before the effectiveness of the effectiveness of different approaches can be program becomes apparent. It is relatively determined at State and national levels by common for short-term monitoring to con- comparing local-scale management pro- clude, incorrectly, that no change has grams. To make this comparison, the total occurred in response to a management pro- costs of carp control need to be measured, gram. Hence monitoring programs need to including both monetary costs and the con- be carefully designed to take account of site tributions of time and equipment by partici- and seasonal variability, time lags and flow pating groups. The cost of developing new events when determining if a carp control control techniques are usually high and program is achieving its defined objectives. these costs also need to be included in cost–benefit analyses for carp control In most cases it will not be possible to assess (Appendix A). a program by referring to experimental control areas without carp. Rather, a useful basis for comparison will be other areas where carp are not controlled or levels of damage recorded at the site before carp control start- ed. Often assessments of the effectiveness of existing programs are based on uncertain or equivocal evidence. Evaluations will be more sound if data from designed monitoring programs running over several years are available.

Managing the Impacts of Carp 155 8.6 Case studies

8.6.1 Carp in a confined wetland ar ea — Pilby Cr eek

Box 9: Best practice management of carp in a confined wetland ar ea Carp are perceived by many in the com- lack of riparian vegetation and cattle were munity to be a major cause of the decline not an issue. of native aquatic vegetation and a reason Should it be possible to eradicate carp for the decline in numbers of waterbirds. from the Pilby Creek billabong, a sec- This case study is based on a wetland with ondary problem of preventing carp from carp present and efforts by a cooperative re-entering the wetland would need to be group to control carp populations and addressed. restore the wetland vegetation to more natural conditions. Pilby Creek is near Lock 6 on the Murray River, near Berri in Site description South Australia. A project of restoration The Pilby Creek Project is regarded as an was initiated by the Renmark Berri Branch experimental site to investigate the effects of of the South Australian Field and Game carp removal. Artificial refilling of the wet- Association and became a cooperative land is made possible by the proximity to effort with the Murray–Darling Association Lock 6 on the Murray River which allows and Riverland Fishermen’s Association. water to enter via a channel above the wet- Being public land, support was needed land. In addition, draining is possible via from the Department of Environment, Pilby Creek. The area is remote, fenced and Heritage and Aboriginal Affairs as the land locked from the general public, reducing managers and from South Australia Water the chance of public interference. as the water managers on behalf of the Murray–Darling Basin Commission. Objectives Defining the problem The objectives of the Pilby Creek Project are to: Pilby Creek wetland is an old billabong of approximately 17 hectares, and is consid- • enhance the ecology of the wetland ered to be an area of high value for native adjoining Pilby Creek in the absence birds and fish. Carp moved into Pilby of carp Creek during floods from nearby rivers. After carp numbers increased, the aquatic • restore the wetting and drying cycle of vegetation and water quality decreased, the wetland and prevent carp from and this was thought to be the cause of a returning on refilling decline in native plant and bird species (Forbes 1995). There was public concern • restore the aquatic vegetation in the for natural conservation values, with carp wetland for its conservation value being perceived to be the greatest cause of the decline in ecosystem health. • increase the bird numbers visiting the Opportunities for duck shooting and an wetland for their recreational hunting area free of carp for aesthetic values were value which may also bring an eco- important to the local community. The nomic gain to local businesses. major limiting factors for the health of the ecosystem were water regulation and carp. Other factors such as nutrients, fishing,

156 Bureau of Rural Sciences Economic gains will be minimal because Implementation the main objectives of the project are to protect and enhance conservation values, As Pilby Creek wetland is a public water- with increased tourism as a secondary body, benefits of its management to meet benefit. The site work may also have value conservation goals accrue to a wide range as an experimental model for carp control of people who may be able to contribute in other areas. to the cost and effort. Costs include: • capital work to drain the area Management options • establishing natural or artificial refill- One-off management options to meet the ing above objectives by reducing carp numbers include: • erecting exclusion screens • poisoning • assessing any habitat changes. • a single event of draining The Pilby Creek Project began in 1989 with • removal by commercial or recreational a plan and several funding bids prepared fishers. by volunteers and staff from the Murray–Darling Association and South Following the removal of carp by any of Australian Department of Fisheries. the above one-off control options, further Funding of $9470 was provided through one-off control options could then be used the Natural Resources Management to prevent adult carp re-entering the wet- Strategy (NRMS) in 1992 to prepare a man- land by installing a gate, screen or other agement plan. The partnership between exclusion devices. Preventing access by community groups with financial support eggs and juvenile carp could be more diffi- from government agencies is useful as it cult. Another option for sustained control provides both financial support, communi- would be to maintain artificial drying and ty ownership and volunteer labour. A fur- wetting cycles. The wildlife and vegetation ther $83 200 funding from NRMS was used enhanced by these options, however, to construct a control drain at one end and would need to be more important than the install screens to exclude fish at the other native fish habitat and nursery areas likely end. In 1993, the billabong was drained to be lost by preventing access by native and commercial operators removed 1200 fish. carp and 1000 native bony herring (Nematalosa erebi). Carp density before Management strategy and after removal was not estimated. Before refilling, screens were placed The control options selected as being the across the intake to prevent recolonisation most likely to succeed, operationally effi- by carp. cient and environmentally effective were drying the wetland to remove fish, followed by the installation of barriers to exclude adult fish. A team consisting of several stakeholder groups was engaged to drain the wetland, screen and refill it.

Managing the Impacts of Carp 157 A further $7200 was received in 1995 for The use of community groups in urban ongoing management and monitoring and wetland rehabilitation has been reviewed $3600 was received in 1997 from the by Dance (1997), who concluded that local Commonwealth Fish Care Program people are vital in determining whether (Natural Heritage Trust) for monitoring. positive or negative changes actually Total funding for this project over ten years occur. Dance suggests that any lead agen- totals $103 520 and has been assisted by cy should have long-term interactions with in-kind support of agencies, volunteers user groups to ensure that banks and vege- and commercial fishers. Carp removal was tation are not trampled and that pest fish sustained for five years but ongoing funds species are not reintroduced. Evaluation of and volunteers are needed to maintain reg- periodic monitoring over the long term is ular artificial draining and refilling to main- required to determine if rehabilitation tain the vitality of the wetland (Brock et al. goals are being met. Long-term monitoring 1994). is still needed to ascertain whether the native vegetation continues to recover. Defining performance indictors The results of this project are confounded There should be an evaluation of recovery because several management options from the original problem to assess the (removal of carp, removal of native bony success or failure of the program. Water herring and alteration of hydrology) plants could be assessed as recovering by were all implemented simultaneously. a measurable amount. This could involve Unfortunately, interpretation of the results measuring the number of plants of signifi- is even further complicated by the lack of cant species or estimating the area covered comparative data on the condition of the by a plant community at a suitable time. wetland before the management plan was implemented. It is therefore not possible No photographic records or base-line data to attribute changes in vegetation to carp are available on the wetland condition removal alone because the effects of the prior to carp to evaluate the success of other options cannot be isolated. This restoring the wetland by excluding carp problem highlights the need for profes- (Roberts and Ebner 1997). These would sional advice on management plans and have been useful to assess the effective- designs for monitoring and evaluation ness of any experimental restoration. before plans are implemented.

Monitoring and evaluation Other considerations Despite a lack of pre-treatment data, the In developing similar agency or communi- performance of the experiment, in particu- ty group partnership projects the following lar water quality and amount of vegetation, issues may need to be considered: was observed by members of the community groups (Forbes 1995). Regeneration of • ability of the wetland to dry naturally native plants was also observed (Forbes or the need for artificial draining and 1995). However, full assessment and moni- refilling toring is needed to determine success. Volunteers continue to supervise draining • is the water body small enough to be and refilling of the wetland and observe contained to prevent the easy changes in the wetland. The results from recolonisation by carp that year showed a reduction in turbidity, increases in abundance of ribbonweed • possibility of major floods which (Vallisneria spp.) and increased density of would reintroduce carp other macrophytes and macroinvertebrates compared to the untreated site (Schiller 1996).

158 Bureau of Rural Sciences • accessibility of the habitat to unin- beds. In 1997, 10 000 carp were killed in the formed recreational fishers who might drying lake (I. McLachlan, Secretary, accidentally reintroduce carp Victorian Field and Game Association, pers. comm. 1998). After the lake was inundated • accessibility of the habitat to commer- again in June 1997 there was evidence of cial fishers and markets to assist in regrowth of plants. Current management removal of carp focuses on maintaining low water levels to allow plants to regenerate and monitoring • skills of volunteer groups carp numbers. The project is considered a success by stakeholders who are represent- • possibility of educational institutes, ed on a Steering Committee which now government agencies and community manages the project (I. McLachlan, groups assisting in monitoring Secretary, Geelong Field and Game Association, Victoria, pers. comm. 1999). • influence of other factors such as In Gippsland in Victoria, the Bairnsdale nutrient inputs, altered hydrology, Field and Game Association began a similar lack of riparian vegetation, catchment project in Macleods Morass, a large Ramsar- clearing and the presence of cattle, all listed wetland near the town. The wetland of which may have contributed to the naturally dried for the first time in possibly original problem. 80 years during the drought of 1996–97. A commercial operator with a seine net removed several tonnes of carp from a A decision to proceed with carp manage- remaining waterhole. A screen was installed ment will be strongly influenced by the across the main channel to the Mitchell natural conservation value of the proposed River with assistance from a number of com- management unit. An estimate of the habi- munity groups and a grant of $10 000 from tat value for native fish is particularly the State government. A partnership began, important if fish are to be excluded. The with cooperative community funding Pilby Creek Project includes a plan to through the Natural Heritage Trust of eventually stock native fish. Field and $39 000 for monitoring and assessment of Game Association groups see the Pilby this site and a seagrass area in Jones Bay, Creek Project as a model for control of Gippsland Lakes. The project includes an carp in wetlands that are valued for water- experiment to assess the levels of damage birds and game birds (Section 4.9). with and without carp. Other cases Other groups have attempted similar programs but a cost–benefit analysis may be needed if evaluation of best management practice is to be undertaken. The Geelong Field and Game Association drained Reedy Lake near Leopold in Victoria in 1996 and made a channel to the Barwon River. A water regulator and a fish screen were installed. The cost of $16 500 came from a community group. Regimes of drying and refilling can assist in carp control. Reedy Lake had been maintained with high water levels since the 1970s and carp had gradually increased in numbers and in the 1990s were damaging Phragmites and Typha

Managing the Impacts of Carp 159 Enhanced wetland in an anabranch of Pilby Creek following carp removal and refilling three times. Source: A. Brumley, East Gippsland Institute of TAFE.

Aluminium screens to restrict carp movement into Macleods Morass. Source: A. Brumley, East Gippsland Institute of TAFE.

160 Bureau of Rural Sciences 8.6.2 Rehabilitation of a small upland str eam — Little Moe River

Box 10: Best practice management of a small upland str eam This case study is based on a small upland stream in Gippsland in Victoria, the Little Moe River, which contains a desirable native fish species as well as carp. The river is undergoing restoration to natural conditions, and the success of restoration is an example of a cooperative venture undertaken by the Settler’s Creek Landcare Group, Waterwatch, the Catchment Management Authority and Freshwater Ecology in the Department of Natural Resources and Environment. Benefits of restoration have been recognised both to the stream reach being rehabilitated and to the habitat downstream through improvements in water quality. The removal of carp is seen as an important aspect of this restoration.

Defining the problem Figur e 21: Little Moe River, Victoria, undergoing The Little Moe River and its tributaries flow restoration to natural conditions. through land used primarily for dairy cattle Clogging of the substrate by fine sediment grazing (see Figure 21). As a result of this removes spaces between particles (gravel intensive land use, extensive clearing of and cobbles) which are used as habitat by native vegetation including riparian zones, juvenile fish, small fish species and stream has occurred. This alteration of streamside invertebrates. Eggs deposited in gravel sub- vegetation, combined with the effects of strates can be smothered by sediments. unrestricted stock access to the stream Species such as river blackfish lay adhesive banks and bed, has been largely responsible eggs requiring clean sites for attachment and for the degradation of instream habitat with- if these sites are covered by sediment, in this region. This habitat deterioration has spawning may not be possible or may be in turn led to the disappearance of a number unsuccessful (Koehn and O’Connor 1990b). of native fish species which were once abundant in this area. One such species is Despite general habitat deterioration the river blackfish (Gadopsis marmoratus) caused by a range of factors, the removal which, according to anecdotal reports, was of carp was considered to be important for abundant in many of the waters within the restoring both water quality and the diver- region until about 40 years ago. River black- sity of freshwater fauna. fish are an important species for both conservation and recreational fishing. Carp are Objectives perceived to have contributed to this decline • to eradicate carp from a section of the through their effects on water quality and Little Moe River increased sediment disturbance. Settling sediments fill pools and holes • to improve native fish habitats scoured in the river bed, decrease substrate • to improve populations of river black- variation and reduce useable habitat areas. fish.

Managing the Impacts of Carp 161 Management options Management implementation One-off eradication from a confined area A small instream barrier was constructed to combined with sustained control to pre- restrict the migration of carp upstream. This vent recolonisation and some targeted was similar to one used successfully in the habitat management. Upper Goulburn River system to exclude trout (Salmonidae) from habitats supporting Carp eradication — as many of the highly a small threatened native species (Raadik technical options for carp control are not and Saddlier 1996). After the barrier was yet available (Chapter 7), only physical constructed, carp were removed from control options are possible. As the stream waters upstream using intensive portable is small, commercial eradication is not eco- backpack electrofishing techniques which nomically viable, recreational removal is selectively remove carp and allow river unlikely to be sufficient and chemical poi- blackfish to be returned to the stream soning was not deemed suitable because unharmed. Ninety-seven carp ranging in of the collateral damage it would cause to size from 67 grams to 5.9 kilograms were desirable species. Therefore, removal by removed from 22 sites in the upper Moe electrofishing was considered the most River system. An additional 30 carp were suitable option. A downstream barrier was removed during an electrofishing demon- then installed to prevent recolonisation. stration conducted for stakeholders. It is Riparian revegetation — efforts (made pri- considered that as carp were in relatively marily over the last ten years) by local low numbers, all carp were removed, but Landcare groups to improve riparian vege- follow up surveys are planned to ensure tation and water quality have been signifi- this. cant. Extensive stretches of stream banks have been fenced, restricting the access by Performance indicators cattle to stream banks, and riparian vegetation has been planted over more than It is expected that the above activities will three kilometres of stream length. Fencing, result in: in conjunction with natural and assisted • improved water quality through revegetation, has led to improvement in reduced turbidities in the Little Moe both water quality and the quality of River and downstream instream habitat. Habitat improvement — it is important to • improved habitat quality within the improve the instream habitat for fish, espe- Little Moe River through reductions in cially river blackfish, by adding logs, areas sediment and increased areas of branch piles and woody debris. aquatic vegetation and woody debris Eventually, this will occur naturally from the re-established riparian vegetation • increased diversity through increased zones as they mature. number of species and abundance of Blackfish reintroduction — river blackfish native fish, aquatic flora and aquatic are currently being reintroduced into this macroinvertebrates reach of the Little Moe River under a Fishcare and West Gippsland Catchment • reduced carp numbers in the Little Management Authority project. Moe river.

Water quality (including water temperature, pH and turbidity), aquatic vegetation and woody debris areas will be measured, sedimentation will be visually assessed and fish and aquatic macroinvertebrates

162 Bureau of Rural Sciences Monitoring and evaluation Improvement in river blackfish abundance and fish habitats will be assessed through Project success will be monitored through follow-up surveys within the creek system the Waterwatch program which operates by Freshwater Ecology, Department of throughout the Moe River system, involv- Natural Resources and Environment. ing the local Nilma and Darnum Primary School students. Through systematic The specific benefits of carp removal alone recording of water quality in the Little Moe cannot be assessed because three other River and surrounding waters, the management options were implemented at improvement of water quality will be mon- the same time. itored in both the short and long term. This will allow any changes in water quality to be identified following carp removal.

Managing the Impacts of Carp 163 8.6.3 National appr oach to carp management in Australia

Box 11: Best practice national carp management

This case study outlines a hypothetical Objectives best practice approach to a national strategy to carp management. Even though costs of direct and indirect damage caused by carp have not been esti- Defining the problem mated, these are likely to be relatively large. Invoking the precautionary principle As the range and abundance of carp has (Intergovernmental Agreement on the increased, so too has community concern Environment 1992) dictates that action to over the ecological damage — both real reduce those impacts should be undertak- and perceived — caused by carp. Although en as soon as possible, allowing for a later there is now evidence to show the types of assessment to refine the relative costs and ecological damage that carp are capable of benefits of carp management. causing (Section 5.3), the magnitude of their impacts compared with the impacts of Specific objectives include: river flow regulation, dams and weirs, • preventing further spread of carp clearing vegetation, nutrient enrichment and catchment disturbance, is far from • research into the ecology of carp in clear. Nevertheless, many groups — partic- Australia and the development of ularly ecologists, conservationists, land- biotechnical control options holders and fishers — believe that there is enough scientific and anecdotal evidence • rehabilitating Australian rivers to that carp are causing environmental dam- favour native fish species age to justify expenditure on carp control. • strategic control of carp in certain Management plan areas. The Federal Government, through the CCCG, has developed a strategic and tacti- cal approach to carp management in con- Management options junction with both State and community The wide distribution of carp in Australia activities. The rehabilitation of rivers, tar- requires adaptive experimental manage- geted research into the ecological under- ment using different options for different standing of the species and potential circumstances, implemented so that treat- biotechnical control options are being ments and their effectiveness can be moni- funded. This approach is outlined in the tored and evaluated. following strategic management plan. Management objectives for freshwater fish Management strategy in Australia also include conservation of biodiversity, protection of threatened The management strategy will implement a species, communities and populations, coordinated, integrated, strategic national and protection, restoration and rehabilita- approach to carp management using a tion of aquatic habitats. Reducing the wide range of national, State and local impacts of carp may contribute to these agencies. objectives.

164 Bureau of Rural Sciences Implementation Performance indicators Active monitoring of carp populations Performance indicators need to be set for toward the edge of their current range was each objective across each management undertaken and the data were entered into area. a national database. These data, together with population data, were used to devel- Monitoring and evaluation op a predictive model to provide scenarios to manage range expansion. No practical Any expansion of carp populations can be methods for sustained carp control on a determined through fish population moni- large-scale are currently available. toring and reports from anglers. Testing of Research into selected options for biologi- biotechnical control options will be used to cal control was undertaken to provide evaluate the success of this research long-term, effective control options. through field experiments. Rejuvenation of Complete eradication and effective, one- native fish populations is more difficult as a off control were undertaken in smaller iso- long term dataset may be needed to take lated areas, especially in areas of new account of natural variability. Regular base introductions. Sustained control and spo- line monitoring of fish populations are radic control were undertaken in selected required and surrogate variables such as areas, using commercial and recreational improvements in available habitat, access harvesting, poisoning, water level manipu- to habitat and improvements in water qual- lations and improved river flows. ity may be used to measure the success of Commercial licences restricted to certain the strategies implemented. Monitoring and areas were given for a limited 10-year peri- evaluation needs to be undertaken on a sci- od to be reviewed by a scientific panel entific basis through a combined effort of after assessing their use following the State agencies and community participants. development of other control options. Improvements in native fish populations and fish habitats were made through cooperative strategies with State agencies.

Managing the Impacts of Carp 165

9. Implementation

Summary (Section 6.2.1) and the Carp Control Coordinating Group (CCCG) (Section 6.2.2) This chapter focuses on the people and (Figure 22). The NCTF was the first initiative organisations involved with managing the for a national approach and has a role of net- damage caused by carp. These include: (1) working and encouraging development of those involved in carp management at the ideas for controlling carp (Cyprinus carpio) strategic and policy levels of government, (2) including commercial harvesting. The aim of those who conduct strategic research to this group was initially to lobby for govern- assist policy makers, to monitor existing pop- ment action on the carp problem, but its aim ulations or to develop control measures, and is now to provide information to both the (3) a range of people, often working togeth- community and managers and to coordinate er, whose involvement is at the operating other interested groups. The CCCG will link level of implementing and monitoring carp to the NCTF to coordinate activities and management decisions. These range from build upon current research outcomes to Commonwealth, State and Territory agency develop a national strategic approach. Both officers to regional and local community groups use funding from the Murray–Darling groups. As carp occur in public waters, Basin Commission and Commonwealth cooperative approaches to their manage- Natural Heritage Trust (NHT). The NCTF is ment are vital and should be encouraged at also supported and convened by the all levels. Murray–Darling Association. Membership of Carp are widespread in public waters, espe- both groups includes research scientists and cially in south-east Australia, so people representatives from government agencies. involved in implementation of carp man- The NCTF has community members and agement are often responsible for protection stakeholders from regional areas and those of publicly owned natural resources. This concerned with the damage caused by carp. contrasts with the management of most ver- The CCCG has representatives from fisheries tebrate terrestrial pests, where many ani- agencies concerned with government policy. mals occur on private land, and landhold- Both groups will be involved with imple- ers may have either legislative requirements menting strategic direction of approaches to or gain personal economic benefits from carp control. control of the pest. Implementation of carp management is not solely the realm of gov- 9.2 Gover nment involvement ernment fisheries agencies but involves other agencies, regional catchment groups Through their role as legislators and as rep- and a wide range of community groups. resentatives of the wider community, gov- Aesthetic, conservation, cultural, recre- ernment agencies are stakeholders in the ational, commercial and animal welfare management of pest species. As carp mostly values all need to be taken into account in occur in public waters, government agencies implementing carp management. This chap- must have a greater responsibility and influ- ter addresses how public managers and ence in carp management than they do for public stakeholders can implement manage- pest species that occur mainly on private ment options. land. At the national level, the Commonwealth 9.1 National level Government is involved in providing a coordinating role for carp control. This role has At the National level there are two bodies recently been taken on by the CCCG which act to develop networks at the policy (Sections 6.2.2 and 9.1) which will help set level, the National Carp Task Force (NCTF) national priorities for carp control. The

Managing the Impacts of Carp 167 National policy guide Carp Control Coordinating Group (CCCG) • Assessing economic and environmental damage • Ranking, assessing control options • Suggesting future research

Commonwealth Voice of Stakeholders funding National Carp Task Force (NCTF) • Advocates for an integrated approach to carp management and control in Australia • Provides a network for support of user groups • Make recommendations for legislation changes NHT MDBC

Funding Law

State Governments Conservation, land, water and fisheries agencies

• Making and enforcing law • Assessing damage by carp • Research of carp: distribution, population estimates, ecology and biology • Implementing control techniques as appropriate • Funding for priority of control options (for example, New South Wales funding industry incentives) • Liaison with regional authorities

Regional catchment authorities or regional cluster groups

• Report to government agencies and NCTF • Assist funding applications • Prioritise regional problems and damage • Network between agencies

Special interest/action groups Recreational and Universities (local user groups, NHT commercial fishers funded groups, Waterwatch, • Research biology and ecology Landcare) of carp • Determining damage • Assessment of damage • Determining damage • Assistance in population estimates • Assistance in control methods • Harvesting Schools/youth groups • Monitoring environmental changes • Field competitions • Reporting to regional groups • Education and awareness of presence of carp

Figur e 22: Flow diagram of strategic direction to carp control.

168 Bureau of Rural Sciences Commonwealth Government also has a role Chapter 6. These activities range from mini- in environmental management and in fund- mal, to eradicating small, new introductions, ing carp research. Funding is currently possi- to encouraging widespread commercial ble from several potential Commonwealth exploitation. In some States, carp harvesting sources: is an integral component of managing native fish harvesting and conservation. There are • Fisheries Research and Development many other management actions and strate- Corporation — which provides funding gies relating to the natural environment and for commercial fisheries related research waters which can affect carp populations. (Section 10.1) These may include implementing weir policies, wetland policies, floodplain and catch- • Bureau of Rural Sciences (BRS), through ment management plans and water reform the National Feral Animal Control strategies. Program (NFACP) (under the NHT)

• Murray–Darling 2001 FishRehab 9.3 The r egional r ole of Program (under the NHT) — which has extension services and a specific directive to provide funding catchment management for carp research relating to their control. Implementing a strategic approach to pest control usually involves a number of agen- The Commonwealth Government is also cies or groups applying a range of control responsible for legislation that provides techniques. Any widespread control mecha- import restrictions (Section 6.2) and strate- nism for carp is likely to involve new tech- gies such as water reform that can affect fish nologies and processes (Section 7.3) that may populations including carp (Section 6.2). need to be explained and accepted by the wider public before they can be used. ‘As carp mostly occur in public Traditionally, State and Territory extension services have been pivotal in assisting in the waters, government agencies adoption of new technologies and processes. must have a greater A better understanding of the problems that responsibility and influence in carp cause in aquatic habitats is needed to carp management than they do dispel some widespread misunderstandings. for pest species that occur mainly Different extension techniques may be need- on private land.’ ed for different control techniques and for different management goals and scale of operations — national, State or Territory, State and Territory governments, through regional, district or local. As most wide-scale their agencies, currently undertake most control programs will be implemented by carp management and monitoring of carp government agencies, the role of extension populations (Sections 7.1 and 7.2). The role officers is likely to be one of education within of State agencies is generally more active in regions affected by the program. management than Commonwealth agencies and this can vary between areas depending on control priorities and methods. State gov- 9.4 Group for mation ernments have legislation covering carp (Section 6.3; Table 13) and also have a role Because carp populations are widespread, it in extension and public education. Control is important for interested community efforts need to be coordinated nationally, groups to interact to share information and even when they are implemented at State or experiences from different areas. Groups regional levels. involved in identifying the problems caused by carp may also have the ability and desire The various management actions being to assist in the planning, implementation and undertaken by State agencies are outlined in

Managing the Impacts of Carp 169 evaluation of management strategies. New South Wales, the Total Catchment Involving interested groups of people, with a Management and River Management range of skills and expertise in the planning Committees function in a similar way. These process, encourages group ownership of groups may be responsible for interacting management decisions and facilitates group with local planning and State government participation in implementing the plan. planning processes, directing or guiding oth- Ideally, composite action groups are formed ers to undertake projects and taking an active with a mixture of skills, including scientists, role in obtaining funding. technicians, naturalists and local interest Broad community groups are concerned groups as well as managers. Additionally, with possible carp damage as part of other there should be a flow of information water and habitat issues. These groups are between interest groups. For example, either organised from individuals with the NCTF, formed from a range of stakeholders, same interest (for example, Landcare was initiated by participants of workshops in groups) or are facilitated at the government 1994 and 1995 (Section 6.2.1). Scientists level. They form locally and, as stakeholders interested in conservation of native fish are in an area, contribute to decision making included in the NCTF as well as lay people and assist actions. Various participants desire directly affected by the presence of carp in involvement in the initiation and implemen- their environment. Commercial fishers tation of carp management actions. formed a subcommittee of the NCTF to dis- cuss techniques, codes of practice and mar- Groups such as Field and Game kets. A workshop for commercial fishers was Associations, Field Naturalists, Native Fish held in Victoria to assist in their operations, Australia and local schools are concerned in developing markets and value-adding to with constructive action in local situations carp products (G. Gooley, Marine and and work together as volunteers. Other Freshwater Research Institute, Victoria, pers. groups use government financial support to comm. 1998). facilitate community volunteers who can be resourceful and take local ownership of a ‘It is important for interested problem. A paid coordinator, with access to community groups to interact to scientific information and with skills in com- share information and munication within teams, ensures that carp experiences from different and their impacts are addressed in a national context, but at a local scale, and with appro- areas.’ priate information and techniques. In summary, each group has a particular rea- Public authorities and organisations with son for involvement in carp management responsibility for managing public waters and has different resources to implement and water storages where carp occur need to action. Some possibilities are summarised in be involved with carp control measures. Table 16. These bodies usually have a legislative obli- gation to produce catchment management strategies and therefore are indirectly 9.5 Facilitating ef fective gr oups required to consider carp damage in their policy. Ideally there should be integration of strategies across States, shires, boards, gov- 9.5.1 Partnerships ernment departments and authorities to form A unified approach to discussions on carp a coordinated approach for carp control has occurred at the national level (Section within a region. Particular options such as 9.1) with the driving force being a desire to those outlined in Section 8.3, could be imple- manage and control carp. Energy must now mented at local and catchment levels. In be directed to develop best practice options Victoria, Catchment Management Authorities and to foster further partnerships for manag- consist of members representing landhold- ing carp and other environmental problems ers, river and catchment management. In (Section 8.4).

170 Bureau of Rural Sciences Managing the Impacts of Carp Table 16: The role of government agencies and community groups in implementing projects to manage carp impacts.

Group Problems the group aim to Role of the group in Source of funds address in relation to perceived managing carp impacts damage by carp or coordination of control methods National Bureau of Rural Sciences Impact of carp as a vertebrate pest. Develop integrated, strategic National Feral Animal Control approaches to manage the Program under the Natural Heritage impacts of carp. Trust.

Carp Control Coordinating Group Need for a national management Provide coordinating information NHT (1998 for three years) via the strategy on carp control. for carp control to be used as Murray–Darling 2001 FishRehab advice by State agencies. Program. Murray–Darling Basin Commission Impacts of carp on water quality in Environmental rehabilitation and NHT Strategic Investigations and aquatic habitats and irrigation areas; management; carp research and Education Program. decrease in water quality and native their control. fish populations.

Fisheries Research and Development Impacts of carp on other fisheries; Provide funds for research. Government and Industry Corporation need to investigate commercial opportunities of carp. State Government departments such as Loss of native fish and aquatic plants; Enact, implement and enforce the State Conservation, Land, Fisheries, Natural increase in turbidity and decrease in keeping, movement, fishing and Resources (see Chapter 6) water quality; loss of riparian other uses of carp; extension. vegetation; deterioration of natural habitat and water quality; biodiversity conservation. Regional Catchment Authorities Loss of native fish and aquatic plants; Integrated catchment State government and local rates increase in turbidity and decrease in management, policy and direc- water quality; loss of riparian tion. vegetation; deterioration of natural habitat and water quality; biodiversity 171 conservation Source of funds State government and local rates State and national Volunteer, (Natural Heritage Trust). Projects and ongoing action; volunteers and funds for special projects. State governments Local volunteers; group fees, for example, Native Fish Australia; State, for example, Victorian Recreational Fishing Peak Body. Self employed; industry enhancement for some operators in New South Wales. State government and local rates Manage allocation of water resources for irrigation agricultural use; control of carp. Action such as competitions; education; possibility of carp as an angling species. Commercial use of native and introduced fish. Role of the group in Role of the group managing carp impacts Planning and regional economic development. Empowering local people to be concerned and involved in their aquatic environment. Undertaking special projects, for example, protecting and enhancing waterbird habitats. Education on all environmental issues that affect aquatic habitats; use of an integrated curriculum. Problems the group aim to the group Problems address in relation to perceived damage by carp or coordination methods of control Decline in native fish; lack of markets for carp. Erosion in channels; increase turbidity; increase in nutrients; vegetation loss. Decrease in water quality; lack of awareness of presence carp. Loss of aquatic vegetation; decrease in water quality; decline habitat for water birds. of presence an Awareness introduced species and its impacts. Loss of native fish; loss habitat for native fish. Decrease in water quality; decline business and tourism; lack of businesses to utilise carp. Water and Irrigation Authorities Water Group Local shires Community action groups, for example, Waterwatch Special interest groups, for example, Field and Game, Field Naturalists Recreational anglers Commercial fishers (associations and State councils) Schools

172 Bureau of Rural Sciences A development plan was funded under the communicated through pamphlets, talks and National Fish Care Program. It proposed a field days. A more active approach with unique cluster approach for the Western greater involvement is even more likely to Murray region of north-west Victoria and change attitudes (Easton 1998). An example southern New South Wales (Heslop et al. of this approach is a carp project in northern 1998). A group formed from a diversity of New South Wales where participants were regional operators and government support encouraged to take part in fishing competi- agencies would be more active than a simple tions, carp tasting and the production of a network. Such an integrated network would recipe book (Easton and Elder 1997). be better able to achieve both the reduction of carp numbers and the enhancement of ‘The ownership of carp as a native fish populations. The partners and regional or local problem should stakeholders, of up to 260 individuals, would lead to local solutions.’ link and would be likely to benefit from the regional development (Heslop et al. 1998). Further funding would be needed to have a Active participation has been used in com- central project officer as an ongoing facilita- munity groups and by a range of govern- tor. ment agencies. This process was initially demonstrated on a large scale by the 9.5.2 Social principles of Landcare Program which empowered an attitude change and consequent action participation and facilitation (Campbell 1990). This model has been One of the greatest benefits of education and adopted by the Waterwatch Program, a community group awareness is gaining pub- national community-based water quality lic involvement in the management process monitoring program which encourages com- so that they are better informed and can munity groups to develop action plans. The actively contribute. Empowering participants carp catching day in Waterweek (October is part of best practice management. 1998) by Waterwatch Victoria followed the Empowerment of both the community and example in New South Wales (Easton 1998) water managers to undertake carp manage- and could encourage best practice carp man- ment is essential for its success. This type of agement in future local projects (R. O’Kane, involvement begins in school science educa- Waterwatch Victoria and Department of tion by developing an approach to discov- Natural Resources and Environment, pers. ery, followed by more investigative inquiry comm. 1998). A key aspect of Waterwatch is where student involvement is paramount also to develop successful partnerships (Trowbridge et al. 1981). The process of between volunteers and local agencies inquiry identifies a problem, formulates (Rixon 1998). hypotheses, designs investigative approach- The ownership of carp as a regional or local es and tests ideas. problem should lead to local solutions. Involvement in environmental actions is like- Groups can be useful for effective imple- ly to lead to a lasting education and has been mentation of best practice carp management. encouraged in science education (Malcolm Using the social principles of team building, 1989). A problem-solving exercise within the groups can: secondary school biology curriculum led to a • implement changes in attitudes towards carp barrier being erected to a wetland near carp Glossop High School in the Murray Riverland (Schultz 1998). This investigation • take ownership of problems in local and its outcomes drew on existing knowl- public waters edge on carp management and the support of senior school staff. • implement programs with volunteer Government departments have extension energy services in many fields where information is

Managing the Impacts of Carp 173 • investigate other factors relating to conditions of local aquatic habitats and catchments

• encourage other changes in catchment practices

• be part of a coordinated approach at a regional level

• gather data to monitor results of programs to be used for evaluation.

If the level of networking from national groups to regional areas is encouraged there will be a successful transfer of educational and scientific material to be applied in a local context. Ownership of the local problem could lead to local investigations using best practice carp management.

174 Bureau of Rural Sciences 10. Deficiencies in knowledge and practice

Summary Most carp management is currently undertaken by fisheries agencies, who have little A number of deficiencies in knowledge which experience and training in vertebrate pest may affect the management of carp in control, and there is little coordination Australia have been identified. The biology between States or with other agencies. and ecology of carp in Australian environ- Adoption of the national guidelines will ments are not well understood and the effect involve some changes at all levels of man- of carp on the environment and native species agement: National, State, regional and has not been quantified. A lack of objective, local, both within government agencies and quantitative data on the impacts of carp on other stakeholder groups. industries and on the environment poses major problems for determining priorities for carp control. Reliable measures of economic 10.1 Intr oduction and environmental costs will allow evaluation of the efficacy of different control tech- The recent resurgence of interest in the dam- niques and of appropriate expenditure on age caused by carp (Cyprinus carpio) and in control, research, management and develop- carp control has highlighted the limited cur- ment programs. This would also allow control rent level of knowledge of carp in Australian efforts to be targeted to areas of greatest need environments. Whilst many actions and or benefit. knowledge gaps are listed in this chapter, some of these are of greater importance than More information is required on the factors others, and priorities must be given to those that affect carp populations in Australia areas which can do the most to limit damage and how changes in conditions may be caused by carp in Australia. This chapter used to the best advantage in carp manage- examines deficiencies in both knowledge and ment efforts. There are few data on the practice. structure and dynamics of carp populations. Standardised indices of abundance need to Universities, fisheries and natural resource be developed. Such information is vital to agencies, regional institutes and other groups the successful implementation of many con- in Australia have conducted research on carp trol techniques. since the 1960s. There has been an emphasis on identifying impacts of carp, although some There are no reliable data on the cost of research has been directed at control mea- controlling carp in the different types of sures (Chapters 5 and 7). Deficiencies in habitats in which they occur or the costs of research are listed in Sections 10.2 to 10.5. using the different control methods. The Several groups have undertaken a coordinat- costs and benefits of different management ing role to direct carp research. CSIRO and the strategies need to be compared to determine Murray–Darling Basin Commission supported their cost effectiveness. a range of carp research projects from 1992–96 Significant knowledge gaps exist in some of and also linked their results with other groups the possible technical methods for carp con- (Roberts and Tilzey 1997; Roberts and Ebner trol. This is particularly apparent in the area 1997). The Cooperative Research Centre for of biological controls, which may offer some Freshwater Ecology (CRCFE) has undertaken of the most promising options for long-term research through its members: NSW Fisheries, and large-scale control. Further evaluation University of Canberra and the and development of these options is needed. Murray–Darling Freshwater Research Centre. Understanding population dynamics of carp The CRCFE also undertook an analysis of and having the ability to model them is essen- future directions of research (K. Davis, unpub- tial for predicting future outbreaks and the lished report 1997) and will implement future potential effects of wider scale control options. research projects that are pertinent to a strategic approach to carp management.

Managing the Impacts of Carp 175 Future research into carp management may • assess the efficiency of different carp also be funded under the Fisheries Research harvesting methods and Development Corporation (FRDC) although this will only involve the commer- • assess the value of harvesting for provid- cial harvesting aspects of carp management. ing long-term population control Prior to implementing new FRDC projects, a strategic approach was developed at a work- • determine when carp densities are low shop attended by a range of stakeholders enough to reduce damage to acceptable related to fisheries industries (commercial and levels. recreational), scientists and managers. A report identified deficiencies in research and Research into methods to measure and man- how FRDC could best support commercial age carp numbers and their impacts and research and monitoring projects (G. summaries of research currently being Newman, Chairperson FRDC Workshop, undertaken are discussed in Chapter 7. unpublished report 1998). Areas for future work included: The Carp Control Coordinating Group (CCCG) is developing a document, Future • evaluating techniques for carp harvest- Directions for Research into Carp, which will ing and control provide a holistic overview of carp research directions and should prompt more strategic, • information on carp distribution and coordinated research activity. biology for population modelling to A Centre for the Analysis and Management of evaluate a carp fishery and to implement Biological Invasions has recently been formed control measures to incorporate the biological, geographic, economic and information services to improve • estimating and modelling commercial the research base for managing biological yields in carp populations subject to invasions. This venture can bring greater varying environmental conditions cohesion to a multidisciplinary approach to manage invasive species across different • exploring cost-effective methods for ecosystems, for a range of species, including exploiting smaller populations if a carp carp (Professor P.S. Lake, Cooperative fishery is to develop Research Centre for Freshwater Ecology, Victoria, pers. comm. 1999). • studies on value adding and market research to increase the benefits from There is a need for greater education and harvesting a resource that has an inher- extension and coordination of carp management (Section 10.6). There needs to be ently low value greater consistency between States with regard to carp management policy - several • estimating non-commercial benefits of States are currently reviewing their regula- carp control including enhancing native tions and strategies (Chapter 6). There also fish populations. This may ultimately needs to be prioritisation (Section 8.3.3) of have commercial benefits if native carp management, including further spread, species can be restored to support at the national, State and regional level. The increased harvesting. general community has a valuable role to play in early detection of new carp incur- All carp harvesting activities need to be sup- sions, carp removal, habitat management ported by targeted research. In particular, and monitoring of habitat condition. research is required to: • identify efficient fishing techniques which limit by-catch of native species

176 Bureau of Rural Sciences 10.2 Populations, distribution lack of monitoring of carp populations, a lack and abundance of validated methods for determining population age structures, and limited understanding of reproductive strategies. 10.2.1 Futur e spr ead Developments required Deficiency Agencies and funding bodies with responsi- It is likely that carp can tolerate the condi- bility for carp management need to agree to tions of most Australian aquatic habitats. The support long-term data collection on carp recent discovery of carp in Tasmania and and to devise methods for doing so that do their establishment in Papua New Guinea not require excessive resources. Of particu- indicate that carp are still spreading. The lar importance is collecting data on factors highest risk mechanisms, areas for future affecting the age structure of carp popula- spread and the potential impacts of such tions so that key times and conditions for spread need to be identified. Predicting the recruitment can be identified. This includes risks of carp spreading and the damage that long-term age-based data sets of carp popu- may occur, can be used to focus efforts and lations from different regions of Australia set priorities to prevent or control further which will allow state-of-the-art models to spread into areas of greatest risk of harm. be developed for carp populations, their impact, and their responses to management. Developments required Development and use of such models will An assessment is required of the risks of carp enable both research and control efforts to spreading into other catchments within be focussed in areas where reducing the Australia and likely impacts should such damage caused by carp is likely to be achiev- spread occur. This assessment should able. These data need to be used to develop include the mechanisms that exist to spread carp population models that can be used to carp into different habitats through both evaluate the potential effects of different deliberate and accidental means. The risks of management strategies and techniques. Such introductions by coarse and live bait anglers models need to be expandable to account deserve particular attention. The areas where for possible differences in fecundity, spawn- such spread could have the most harmful ing conditions, growth rates and population consequences also need to be identified. dynamics in different climates because it is unlikely that carp populations around Australia all behave in the same way as those 10.2.2 Long-ter m data sets and in the Murray–Darling Basin. models on factors af fecting abundance 10.2.3 Carp biology in Australia Deficiency Deficiency There are inadequate quantitative long-term data on carp population dynamics, growth More information on the basic biology of rates, densities, distribution, abundance and carp in Australia including behaviour, repro- the factors affecting them. These aspects of duction, feeding, migration, social interac- carp biology are likely to vary between differ- tions, and other ecological details is needed ent climatic regions in ways that may influ- for targeting, refining and focussing manage- ence decisions on control methods. Carp ment options more effectively. For example, control is a long-term exercise requiring high it is not known whether carp actually spawn quality data over a sufficient time scale to in flowing water in main river channels in develop reliable and sophisticated popula- Australia. Other deficiencies include aspects tion models to evaluate likely outcomes of of carp reproductive and digestive physiolo- different management strategies. Key impedi- gy that could provide targets for new control ments to obtaining such data have been the methods.

Managing the Impacts of Carp 177 Developments required Developments required Research is needed to address these informa- An assessment of the total market value for tion deficiencies. One obvious need is to existing carp products is required. There is a determine the spawning requirements for need for an economic assessment of export carp in Australian aquatic habitats. Targeted markets and potential value-added products studies are needed to identify possible weak- for which carp can be used so the potential nesses that could be attacked by new control increase for carp markets both in Australia methods. and overseas can be estimated. Marketing assistance may follow this evaluation. The risk that further development of carp har- 10.3 Economic impacts vesting as a commercial industry or for recreational fishing could inhibit the future con- 10.3.1 Impacts on fisheries and trol of carp through claims for loss of income and compensation also needs to be evaluat- other industries ed. Options for managing this risk need to be investigated including the feasibility of incor- Deficiency porating ‘sunset clauses’ into permits for the recreational or commercial use of carp. The impacts of carp on native fisheries (both commercial and recreational) and other industries are not well understood and 10.4 Envir onmental impacts hence it is difficult to assign priorities to carp management actions to minimise impacts. Knowing the costs and impacts on fisheries 10.4.1 Identifying envir onmental and other industries will allow for control impacts techniques to be focused in areas where damage can be minimised cost effectively. Deficiency Developments required The environmental impacts of carp in Australia are largely unknown. In particular, Knowledge of the density–damage relation- little is known about the interactions ships of carp and their impacts and cost to between carp and native fish species, densi- fisheries and other industries (Section 5.2), ty–damage relationships between carp and particularly impacts on: environmental variables (for example, water • individual fisheries, especially those quality) or the effects of carp on most aquatic habitats. An understanding of the interac- identified by commercial fishers to be of tions of carp with the environment and high priority native aquatic species is necessary so that management options can be focussed to • water turbidity reduce harm to acceptable levels in areas with the highest environmental values. This • irrigation pumps and channel banks. will allow the type and location of impacts of carp to be estimated and will assist strategies to reduce them. Understanding of carp 10.3.2 Carp as a r esour ce impacts will enable better assessments of the risks posed by carp expanding into new Deficiency habitats. Knowledge of the damage carp cause and density–damage relationships will There has been little development of mar- allow the most cost-effective management kets and products for use of carp in options to be determined and will help allo- Australia. Information on the resource value cate priorities to minimise damage to areas of carp will allow better decisions to be of greatest importance. made on carp control based on cost-benefit assessments.

178 Bureau of Rural Sciences Developments required Developments required Scientifically validated studies of the impacts Controlled, replicated experiments that test of carp on a wide range of environmental the impact of carp over a range of environ- variables are required, particularly to: mental variables and measure the recovery of ecosystems following carp reduction or • quantify interactions between carp and eradication. native fish communities and species

• quantify changes that carp cause to 10.5 Population contr ol other animal communities, such as zoo- techniques plankton, macroinvertebrates, amphibians, reptiles and birds 10.5.1 Infor mation to deter mine the • quantify the damage that carp cause to a feasibility of contr ol options range of aquatic habitats in Australia (for example wetlands) Deficiency

• determine the levels to which carp need There is often insufficient information to to be reduced to reduce environmental determine whether carp eradication and/or damage to acceptable levels damage reduction is an achievable objective in different habitats in Australia. The six fea- • determine the degree of recovery which sibility criteria developed by Bomford and is possible by controlling carp and its O’Brien (1995) for successful pest eradica- significance with respect to other tion are outlined in Section 8.3.2. Choquenot degrading factors and Parkes (in press) have examined models for setting thresholds for pest control effort • assess the economics of environmental in relation to target pest densities and levels of resource damage. There are often inade- damage caused by carp. quate data to make reliable assessments on the resource protection benefits of carp control or the feasibility of carp eradication. 10.4.2 Measuring impacts and r ecovery Developments required

Deficiency In areas where carp control is to be undertaken, balanced, reliable data on the criteria The problems of measuring the impacts of that will determine whether the control pro- carp and the techniques to do so are dis- gram objectives can be met need to be col- cussed in Section 7.1. There is a particular lected and evaluated. need to quantify environmental impacts and be able to make reliable predictions on dif- 10.5.2 Envir onmental r ehabilitation ferent scales across the distribution of carp in Australia. A better understanding of impacts Deficiency and recovery is needed to enable realistic management objectives to be developed and There is evidence that aquatic ecosystems monitoring programs to be designed that close to their natural condition, and which measure appropriate performance indicators have intact native fish communities, are able are also required. to limit increases in carp populations. However, the reverse situation, that rehabilitation of degraded ecosystems can reduce established carp populations, has not been tested. Many ecologists and conservationists

Managing the Impacts of Carp 179 consider environmental rehabilitation is like- scientific trials have been conducted in ly to offer benefits for carp control (Section Australia to determine the level of carp con- 4.4). Rehabilitation research is needed to trol afforded by manipulating food chains. determine whether this approach has potential as an option for carp management. Developments required

Developments required Experiments using different densities of native predator species need to be conduct- Rehabilitation sites should be established ed in enclosed waters to assess the impact where environmental attributes that make on different carp population densities and conditions less favourable for carp, and changes in carp numbers and habitat condi- which are likely to enhance native fish num- tions over time. The size and effectiveness of bers, can be experimentally manipulated. fish stocked and the time required to estab- Carp populations and natural biota need to lish effective predator populations also need be monitored to measure responses to reha- to be assessed. bilitation and the efficiency of reducing carp Many biomanipulation approaches can be impacts. Realistic time frames must be con- combined with conventional control meth- sidered for this option. ods to get the most benefit. For example, large numbers of carp are removed by con- 10.5.3 Envir onmental manipulation ventional means and then predators are (drainage, water level stocked to keep the remnant carp popula- fluctuations) tion under control. The effectiveness of these treatment combinations of conventional and Deficiency new technologies needs to be evaluated.

It is likely that environmental manipulations, 10.5.5 Chemicals such as changes to water levels and environmental flows, can be used to control carp but Deficiency this approach has not been evaluated on a large scale. The impacts of such environ- There is currently no method of chemical mental manipulations on other species have control that is specific to carp. In addition, also not been evaluated. currently available chemicals are either in limited supply or too expensive for large- Developments required scale application. Improved delivery methods and chemical specificity will increase the Effects on carp populations of manipula- feasibility of using chemicals as a carp man- tions, such as increasing or decreasing water agement option with fewer environmental levels or total drainage, need to be moni- risks and reduced costs. tored and evaluated. The cost of this approach, in terms of native flora, fauna and Developments required habitat characteristics needs to be assessed simultaneously. Improved delivery methods for existing poisons may reduce the quantity and cost of 10.5.4 Biomanipulation product needed to treat a specified area. Refined delivery methods may make non- Deficiency specific poisons more specific to carp. One example is the delivery of rotenone in a Predation on carp, especially young fish, by flavoured pellet bait which attracts carp only. native piscivorous species such as Murray Other poisons may be developed that kill cod (Maccullochella peelii peelii) and golden carp without harming native species. All new perch (Macquaria ambigua) has been delivery methods and new poisons will recognised by fish ecologists (Section 7.3.6) require extensive testing. as a potential carp management option. No

180 Bureau of Rural Sciences 10.5.6 Biological contr ol using Developments required viruses The feasibility of developing molecular approaches for wide-scale carp control in Deficiency Australian conditions needs to be investigated. To assess the potential use of viral control agents, such as Spring Viraemia Carp Virus 10.5.8 Effects of multiple contr ols (SVCV), it is important to understand methods of application, limitations and risks. Deficiency There is little information on the behaviour of fish viral agents, including their transmis- The benefits of pest control can theoretically sion between individuals. The effects of be multiplied by simultaneously applying SVCV on Australian carp populations under more than one form of control (Section 7.3). Australian conditions are not known. Key However, limitations in development of indi- questions which need to be answered in vidual control methods has largely prevent- regard to SVCV in Australia have been out- ed evaluation of multiple control options lined by Crane and Eaton (1997) (Section that may offer increased effectiveness with 7.3.5). If biological control using viral agents potential cost savings. is technically feasible, and socially and economically acceptable, it could provide sus- Developments required tained carp control at relatively low cost. Experiments and field trials are needed to test combinations of control techniques at an Developments required appropriate scale. Examples might include Research is needed to determine the poten- commercial harvesting of adults from a river tial for SVCV or other viral agents to control reach combined with poisoning off-channel carp under Australian conditions and the wetlands to remove juveniles or poisoning a potential risks for non-target species. The lake followed by predator stockings. social perception of viral control, and international trade implications, will also need to 10.5.9 Exclusion barriers be addressed before viral control can be attempted. Deficiency

10.5.7 Contr ol using molecular Barriers in the form of ‘fish screens’ have appr oaches (chr omosomal been used to exclude carp but their success has not been determined. Screens may pre- manipulation, gender vent the movement of larger fish, but eggs, manipulation, inducible larvae and juvenile fish may easily pass fatality genes) through. Further options to improve screen design could be investigated. The effective- Deficiency ness of acoustic and electric barriers in excluding carp has not been tested. Fish bar- Molecular approaches may provide opportu- riers have potential as cost-effective, envi- nities for cost-effective, wide-scale carp con- ronmentally friendly methods of carp man- trol, but there is a need for further develop- agement to assist one-off or sustained man- ment and testing. Many of these require- agement applications. ments have been outlined by Grewe (1997; Section 7.3.8). Developments required Testing of physical and acoustic and electri- cal barriers for all sizes of carp is needed.

Managing the Impacts of Carp 181 10.5.10 Carp harvesting because of inadequate monitoring and evaluation. Proper monitoring and evaluation of Deficiency the effectiveness of control techniques will enable improved methods and approaches Environmentally friendly and efficient meth- to be developed so that the effectiveness of ods of carp harvesting in a range of habitats carp management in Australia can be contin- are needed. ually improved. Monitoring and evaluation will also allow cost savings by discontinuing Developments required inefficient or ineffective methods. Targeted research into by-catch, environ- Developments required mental damage, efficiency and effectiveness of carp harvesting techniques in providing Operational monitoring, to assess the effi- long-term reductions to reduce damage to ciency of the operation, performance moni- acceptable levels. toring, to assess the effectiveness of the management plan, and evaluation need to be integral components of all carp control pro- 10.6 Management grams. As part of this, simple standardised monitoring methods need to be developed and promoted to allow better comparison of 10.6.1 A coor dinated, national results over time and between regions. This education campaign will enable managers to assess whether they are achieving carp damage-control objec- Deficiency tives efficiently. The general public and community groups interested in carp control are not well- 10.6.3 Management zones informed about current developments in carp control techniques and management, Deficiency with the result that local efforts lack coordi- Most current carp management is undertak- nation. Improved understanding by the pub- en by State and regional agencies (mainly lic of the biology of carp, possible manage- fisheries agencies) with little coordination ment techniques and the value of coordinat- between States or agencies. A coordinated ed management based on best practice prin- system of management zones will allow ciples, pest management principles and par- more efficient strategic planning, better risk ticipation of all stakeholders, will engender assessment and systematic implementation support for carp control activities. and evaluation of management programs to control damage caused by carp. Developments required A national, coordinated communication and Developments required education strategy and campaign aimed at The feasibility of establishing carp manage- improving the knowledge of all stakeholders ment zones which do not coincide with local and the general public of carp and their shire or State boundaries needs to be evalu- impacts. ated. For example, a zone system based on existing classifications of river drainage divi- 10.6.2 Effectiveness of curr ent sions, catchments, and sub-catchments may management allow resources to be coordinated more efficiently. National coordination to develop Deficiency management zones, under the umbrella of CCCG, may assist this. There is a lack of reliable information on the effectiveness of current carp management

182 Bureau of Rural Sciences 10.6.4 Coor dinated infor mation systems

Deficiency Most carp research and management is undertaken by agencies, institutions and community groups with limited exchange of information between groups. With increasing efforts in carp research and management, there is a need for centralised records of work in progress and results achieved to assist with adaptive management, adoption of new techniques and a decreased risk of unnecessary duplication of effort.

Developments required A central database which records details of all carp-related research and management projects, with supporting documents, is needed to facilitate coordination at a national level, and communication at local operational levels. Easy access, for example via the internet (as with the current carp distribution database www.sunfish.org.au/recfish/NCTF/Carpdatabase.htm), with a simple Geographic Information System-based user interface is needed to allow easy updates and dissemination of information. Established groups such as CCCG and the National Carp Task Force are in a good position to be involved in this objective.

Managing the Impacts of Carp 183

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Williams, W.D. (ed.) (1980) An Ecological Basis for Water Resource Management. Australian National University Press, Canberra.

204 Bureau of Rural Sciences Appendix A

Economic strategies for carp For example, if carp are reduced by 50%, management how much will this improve water quality. There may be interactions between pest den- (Bomford and workshop participants 1995) sity and other management practices which need to be taken into account. For example, Water managers who wish to determine the the improvement in water quality caused by optimal economic strategy for managing a reducing carp densities by a certain amount problem caused by carp (Cyprinus carpio) may vary in different habitats. could use the stepwise approach outlined in this appendix. We recognise that often the STEP 4: Estimate the effectiveness of each information necessary to complete the steps control option is lacking. Nonetheless, the exercise of attempting to go through the process, How much will a given effort using a particu- recording the assumptions and making best lar control option reduce pest density? guess estimates, may prove a useful aid to STEP 5: Use the information from Steps decision making for carp management. 1–4 to estimate costs and benefits STEP 1: Identify desired outcomes and of implementing each control estimate a dollar value for each option, including options which of these combine more than one technique Where outcomes are measurable commodi- ties, such as a reduction in water quality to a Costs will be those associated with imple- specified level, this should be reasonably menting control options, and may include easy. Where outcomes are difficult to mea- costs of monitoring carp and planning. sure or intangible, such as reductions in Benefits will be the value of the reduction in numbers of anglers because of large carp damage to resources (that is the value placed numbers, water managers may be obliged to on desired outcomes listed under Step 1). estimate how much they consider is an Different carp management options will gen- acceptable amount to spend to achieve that erate different cost–benefit relationships. outcome. Estimates of benefits and costs can be dis- STEP 2: List all control options and how counted back to net present values (usually much they would cost to imple- using a discount rate equivalent to the inter- ment est rate on financing of the control operation). This will reduce the value of costs and Control options can be different techniques, benefits accruing in the distant future relative combinations of techniques, or different lev- to those accruing in the near future. els or frequencies of application of tech- STEP 6: Carry out a marginal analysis niques (Chapter 7). It is important that the (Figure 23) (A1) options for control are expressed as activities that a manager can select either to do or not Plot both the incremental marginal change in to do. the cost of carp control and the incremental change in the cost of damage caused by carp STEP 3: Estimate the relationship between against the level of carp control contemplat- carp density and damage for ed. Where the two lines cross is theoretically each resource damaged by carp the optimal level of pest control (Hone (see Figure 23, Section 5.4.4) 1994). Further increases in control activity do not cause commensurate reductions in damage, so at higher levels of control beyond

Managing the Impacts of Carp 205 these matrices — what time span is covered and how will this affect costs and benefits? These matrices can then be used to select the option(s) which best meet the manager’s Marginal cost desired outcome. If the manager is risk-averse, of damage the best options will be those that bring in rea- Marginal sonable returns under all conditions. If the cost of control manager’s priority is to maximise profit, the Cost preferred options will be those that are likely to give the highest returns on investment, despite the risk of having no returns or even a loss. Pay-off matrices can also be used by water High Low managers to compare returns on investment in carp Control effort carp carp control with returns on using the money density density for some other purpose, such as increased water treatment. ll dbd Figur e 23 (A1): A marginal analysis as described in Steps 1–7 complete the basic model. The Step 6 (units on the x-axis are level of control effort not carp density). A marginal analysis is an analysis of the model can be made more accurate by adding relative shift in cost and benefit values that occur as additional features. Incorporation of such fea- incremental changes are made in the level of pest con- tures will make it more complex, but including trol effort. at least some of them may be necessary to make the model accurate enough to be useful. this point, costs will exceed savings in Some additional features that might be worth reduced damage. including are: The problem for carp managers is that • social benefits in Step 1, such as increased because they often do not have good infor- biodiversity and threatened species pro- mation on the damage–density relationship tection, better water quality, increased it is hard to estimate the optimal control angling opportunities, and retaining rural point. Further, even if they can make a good tourism guess, it is not usually practical with most control techniques to simply cut off control • risk management for potential spread of efforts at some pre-determined carp density. diseases by carp to native species It is preferable to have a range of control options ranked along the x-axis, with their • effects of government intervention on associated cost and benefit values for imple- costs (in Step 2) such as tax incentives or mentation, so a manager can select which direct assistance with implementing carp option is optimal. For example, number of control removal runs by electrofishing could be put along the x-axis. • commercial harvest of carp as an alternative control could be included as an Construct a table listing all the STEP 7: option in Step 2 control options and their associated costs and benefits (this is • indirect effects of pest control, for exam- called a pay-off matrix) ple, the effects of carp control on Murray Managers may wish to construct different cod numbers could be included as an matrices for different conditions, such as dif- interaction in Step 3 ferent removal rates, seasonal conditions or water quality values. Managers will also need to consider time-scales when constructing

206 Bureau of Rural Sciences • the form in which benefits come may be significant to the manager (Step 5). For example, it may be more attractive to remove carp commercially than to address more damaging and expensive environmental problems.

Much of the information needed to follow the steps outlined above is not available. Appropriate levels of control required to reduce some of the environmental damage caused by carp cannot be determined because the cost of the damage is intangible. While some techniques are available which attempt to quantify such intangible effects (Braysher 1993) these are complex and expensive to use and of limited reliability. Despite these problems, the steps outlined above, especially Steps 1–5, enable managers to assess the most appropriate actions to achieve the desired reduction in damage

Managing the Impacts of Carp 207

Abbr eviations and Acr onyms

ACF Australian Conservation CRCFE Cooperative Research Foundation Centre for Freshwater Ecology AFCAA Australian Federation of Coarse Anglers Association DPI Department of Primary Industries AFFA Agriculture, Fisheries and Forestry – Australia EA Environment Australia ANZECC Australia and New Zealand EFSC Exotic Fishes Sub- Environment and Committee of ASFB Consultative Committee ESD Ecologically Sustainable AQIS Australian Quarantine and Development Inspection Service FRDC Fisheries Research and ARSFC Australian Recreational and Development Corporation Sport Fishing Confederation FWAA Far West Anglers Association Australian Society for Fish ASFB Geographic Information Biology GIS Systems Australian River Assessment AusRivAS Inland Fisheries Commission Scheme IFC IFG Inducible Fatality Gene BACI Before-After-Control-Impact ISG Inducible Sterility Gene BRS Bureau of Rural Sciences Land and Water Resources Conservation and Land LWRRDC CALM WA Research and Development Management, Western Corporation Australia Ministerial Council on Centre for the Analysis and MCFFA CAMBI Forestry, Fisheries and Management of Biological Aquaculture Invasions MDA Murray–Darling Association CARP Carp Assessment and Reduction Program MDBC Murray–Darling Basin Commission CCC Community Consultative Committee MIA Murrumbidgee Irrigation Area CCCG Carp Control Coordinating Group NCTF National Carp Task Force CIT Canberra Institute of NFA Native Fish Australia Technology NFACP National Feral Animal CMAs Catchment Management Control Program Authorities NHT Natural Heritage Trust Carp Production Incentive CPIS National Management Scheme NMSCC Strategy for Carp Control CPUE Catch-Per-Unit-Effort NRMS Natural Resource CRC Cooperative Research Management Strategy Centre

Managing the Impacts of Carp 209 NTU Nephelometric Turbidity Units PIRSA Primary Industries and Resources South Australia QAP Quality Assurance Program QFMA Queensland Fisheries Management Authority RAA Recreational Anglers Association Ramsar See Glossary RecFish Formerly Australian Recreational and Sport Fishing Confederation. SAFGA South Australian Field and Game Association SARDI South Australian Research and Development Institute SCARM Standing Committee on Agriculture and Resource Management Sp. Abbreviation for an unnamed species Spp. More than one species of the genus SVCV Spring Viraemia of Carp Virus VRFish Victorian Recreational Fishing Peak Body VPC Vertebrate Pests Committee

210 Bureau of Rural Sciences Glossary

Acclimation: The process of allowing ani- Basin: An area in which the ground level mals to become accustomed to experi- dips from all directions towards a com- mental conditions, usually in an artifical mon central point. A river basin is the area environment such as aquaria where tem- drained by a river and its tributaries. perature, lighting or water quality are artificially maintained. Benthic: Living on or in the bottom of a water body, bottom living. Acclimatisation: The process by which animals become accustomed to a change in Benthivor ous: Animals that feed on the ani- natural environmental conditions, such as mals from the benthos. occurs when fish are transferred from one river system to another, or as a result of Benthos: Animals living on or in the sedi- seasonal climatic changes. ment at the bottom of a water body. ad hoc: Impromptu or unplanned, refers to Billabong: Typically ox-bow lakes which management of problems reactively with- are cut off from river channels, but also out reference to a strategic plan. refers to other naturally-occurring floodplain waterbodies. Adipose fin: Small, fleshy rayless fin on the posterior dorsal surface of ‘primitive’ fish Biofilm: The thin film of biological material, like salmonids. such as bacteria and algae, that grows on submerged surfaces. Algae: Single-celled, colonial or filamentous aquatic plants, distinct from vascular Biological contr ol: The use of living organ- plants. isms to control pests or diseases. This may involve the release of a natural or geneti- Alluvial plain: An area of fairly flat land cally modified organism. where a river has deposited silt. Biomass: The weight of living material. The Anabranch: Branch of a river which leaves total weight of all organisms in a particular the main channel and may rejoin further habitat or area. downstream. Biota: All living organisms, usually used for Aquacultur e: The farming of fish or other all the living organisms in a place (for aquatic organisms under artificial condi- example, the Australian biota). tions. Biotic: A descriptor of the living compo- Attached algae: Algae which are attached to nents of ecosystems, (for example, a biotic objects such as rocks, sediments or other response is the response of all or some liv- plants. ing things to a change in some other part of an ecosystem). Barbels: Fleshy, sensory protrusions around the mouth of carp and some other fish. Bloom: Rapid, temporary increase in the pop- Commonly referred to incorrectly as ulation of aquatic photosynthetic micro- ‘whiskers’. organisms (for example, phytoplankton or cyanobacteria) to the extent that the water becomes discoloured and, if the micro- organisms are toxin producers, unfit for drinking.

Managing the Impacts of Carp 211 Brackish: Water with a salinity greater than Cyprinidae: The taxonomic family includ- fresh water but less than sea water, usually ing carp (Cyprinus carpio) and other found in estuaries. species such as goldfish (Carrasisus auratus), roach (Rutilus rutilis), and Car nivor e: An animal that mainly eats ani- tench (Tinca tinca). mals. Dam: A wall or other structure holding Catchment: The area from which a river, water back. stream, lake or other body of water receives its water. Decomposers: Organisms (for example, bacteria and fungi) in an ecosystem which Catadr omous: Describes fish that migrate convert dead organic material into simple from fresh water as adults to spawn at sea compounds that primary producers can (for example, eels). utilise.

Ceratopogonidae: Biting midges, larvae of Delta: A deposit, usually fan shaped, of large which are found in freshwater habitats. amounts of silt at the mouth of a river.

Channel: The part of a stream or river con- Demersal: Living on or near the bottom of fined between banks, or a deeper passage the ocean. through a lake or harbour. Detritus: Organic debris from decomposing Chir onomids: Midges, larvae called blood material. worms, found in aquatic environments. Detritivor e: A consumer organism that Clay: A fine particle of sediment. Finer than directly consumes dead organisms and sand. the cast-off parts and organic wastes of organisms (for example, vulture, jackal, Coarse fishing: A recreational sport that earthworm, termite, millipede, ant, and arose in England and Europe as a ‘gentle- crab). man’s pursuit’, where cyprinids including roach (Rutilus rutilus), rudd (Scardinius Dischar ge: Flow of a river, usually measured erythrophthalmus), chub (Leuciscus in megalitres per day. cephalus) and dace (Leuciscus leuciscus) are caught and released. Discount rate: The rate used to calculate the present value of future benefits or Coastal types: There are three main kinds costs. Discount rates are calculated using of coast in Victoria. These are dominated the reverse equation to that used to calcu- by: cliffs; (sand barriers) beaches and late interest rates on invested money (that dunes; and marshes, tidal banks and man- is, the interest rate is negative). grove swamps. Ecologically Sustainable Development Cobble: Substrate particles with a diameter (ESD): 1992 Brundtland Report by the of 64 millimetres to 256 millimetres. World Commission on Environmental and Development as ‘development which Coleopterans: Beetles. meets the needs of the present without compromising the ability of future genera- Community: All organisms inhabiting a tions to meet their own needs’. common environment and interacting with one another.

Cyanobacteria: Bluegreen algae.

212 Bureau of Rural Sciences Ecology: The study of the interactions of Exploitation competition: Competition organisms with their physical environ- between species where one suppresses ment and with one and other, including another’s rate of increase by prior con- results of such interactions. sumptive use of a limiting resource. For example, carp competing with native fish Ecosystem: A term used to encompass all for food. the organisms (biotic) in a community together with the associated physical Feral: The description given to animal environment (abiotic) factors with which species that are normally domesticated they interact (for example, a rockpool (for example, cats, goats, pigs, horses, ecosystem, a forest ecosystem, a wetland camels and goldfish) but which have ecosystem). reverted to a wild state.

Emer gent vegetation: Vegetation growing Fish passage: Ability for fish to move or protruding above the water surface. unimpeded up and down the river system.

Endemic: Used to describe a species that is Fishway: A structure which provides fish naturally restricted to a particular region passage past an obstruction in a stream. (although it may be able to establish in another region if introduced). Flocculate: The aggregation of particles.

Ephemeral: A term used for organisms with Fluvial: Of, or produced by, a river. short life cycles, usually adapted to making rapid use of favourable environmental Food chain: Pathway of energy. conditions. Food web: The linking and inter-linking of Epifauna: Fauna associated with the sub- many food chains as may be found in a strate surface. complex ecosystem with several trophic levels (for example, lake, eucalypt forest). Erosion: The act or process of eroding, especially the wearing away of the land Fork length: One of the ways to measure surface by sun, wind, water, frost or ice. the length of fish with forked tails, from the tip of the snout to the inside angle of Estuary: The section of a river near its the fork. mouth where river flow meets tidal cur- rents, and where fresh water becomes For m: Particular observable characteristic of saline. variant of a particular individual. The phe- notypic expression of the genetic make- Eutrophication: An increase in the nutrient up. Carp can have a mirror or fully scaled content of a body of water, occurring form. It is possible to have different forms either naturally or as a result of human within the same strain. activities. Eutrophication leads to a rapid increase (bloom) in growth of algae. Gastr opods: Molluscs including snails and limpets. Euryhaline: Able to live in a wide range of water salinities. Genotype: Genetic makeup of an individual.

Gravel: Substrate particles with a diameter range of 2 millimetres to 16 millimetres.

Managing the Impacts of Carp 213 Groundwater: Water that is found beneath Invertebrate: An animal without a back- the surface of the ground, usually in bone (for example, worms, insects, amoe- porous rock known as an aquifer. bae).

Habitat: The place normally occupied by a In-str eam-use: Ways of using water which particular organism group or population do not require it to be removed from the of species (for example, nesting habitat, river or wetland system. freshwater habitat). Ledgering: Method of catching carp used by Hemipterans: ‘True bugs’ such as back- coarse anglers. swimmers and water boatmen. Lentic: Still water systems (for example, bill- Herbivor e: An organism that eats plants or abongs, lakes, wetlands). other photosynthetic organisms to obtain its food. Leptoceridae: Caddis flies which live in cases. Hybrid: Individual resulting from interbreeding of two species, for example, Lotic: Flowing water systems (for example, carp and goldfish. A hybrid needs to be rivers). infertile for the two parents to be regarded as two species. Marginal analysis: An analysis of the relative shift in cost and benefit values that Hydr ology: The study of water on, or occur as incremental changes are made in under, land. the level of pest control effort.

Indigenous: Native, although not necessari- Market failur e: Occurs when resources are ly restricted, to an area. not allocated efficiently through the use of the market, that is, when the costs and Index of abundance: An indicator of rela- benefits to society are not equated by the tive number or density of a species which natural market forces of supply and has a mathematical relationship (usually demand (for example, unsustainable use linear) to absolute numbers or density. of natural resources or development of social inequities). Infaunal: Fauna living in the substrate. Market value: When commodity prices set Inor ganic: Not forming part of the sub- by natural supply and demand have unde- stance of living bodies. sirable social or environmental consequences (for example, unsustainable use Inter fer ence competition: Competition of natural resources or development of between species where one suppresses social inequities). another’s rate of increase by interfering with its ability to procure or use a limiting Macr oinvertebrate: An animal without a resource, or where one species limits backbone (for example, worms, insects) another’s use of a limiting resource, not by visible to the naked eye. prior consumptive use, but through preventing access (for example, through Macr ophyte: Large aquatic plant. behavioural aggression and exclusion). For example, carp competing with native Micr ocrustacean: Very small, mainly aquat- fish for habitat space such as spawning ic, gill-breathing organisms with anten- sites. nae, jointed legs and hard surface skeleton.

214 Bureau of Rural Sciences Oligochaetes: Aquatic worms. Primary salinity: An accumulation of solu- ble salts in soil and water (salinisation) Omnivor e: An organism at the consumer which occurs through natural processes. level that obtains its food energy from both plants and animals (for example, Race: Genetically distinct populations of a humans, feral pigs, carp). geographic region. Species that are now geographically isolated and not able to Organism: Any living thing, animal, bacteri- interbreed with another race, for example, um or plant, whether one-celled or many Chinese and European carp. celled. Ramsar: Convention on Wetlands of Inter- Parasite: An organism attached to another national Importance, held 30 January– causing the host harm. 3 February 1971 in Ramsar, Iran.

Peduncle: The caudal peduncle is the nar- Rechar ge: The replacement of groundwater row part of a fish’s body at the base of the (for example, the recharging of aquifers) tail. by rain or other forms of precipitation. pH: A measurement to indicate the level of Redfin: An Australian common name for acidity or alkalinity of a solution where European perch (Perca fluviatilis) pH 1 is highly acidic, pH 7 is neutral and pH 14 is highly alkaline. Reservoir: A place for storing water or the water which is stored. Phenotype: Appearance of an organism depending on the genotype and environ- Rhabdovirus: The group of rod-shaped ment. viruses that includes the Spring Viraemia of Carp Virus. Phytoplankton: Free-floating, single-celled or colonial algae. Riffle: Relatively shallow, fast-flowing section of a stream where the water surface is Piscivor e: An animal that feeds on fish. roughened and not smooth.

Plankton: Free-floating, mostly microscop- Riparian: Of or on the river bank. ic, aquatic organisms — can be divided into phytoplankton and zooplankton. River: A large permanent stream flow of water in a natural channel with banks, Pock mark: Small depression in bottom which flows into the sea, or a lake. sediments caused by carp feeding activity Saline: Of or containing salt. Population: A group of animals of a particular species occupying an area where they Salinity: The concentration of various salts are subject to the same broad environ- dissolved in a volume of water. mental or management conditions. Salmonids: Trout and salmon species. Potable: Drinkable (water). Salt water intrusion: The movement of Precipitation: The process by which water saline water into an aquifer. falls from the atmosphere, as rain, hail, sleet, snow or dew. Silt: An earthy deposit laid down by a river, lake, or other water body, which is finer Predator: An organism that captures and than sand but coarser than clay. feeds off another organism.

Managing the Impacts of Carp 215 Spawn: In aquatic animals, to produce or Taxonomy: The science of classification of deposit eggs and sperm. animals and plants.

Species: Group of interbreeding individuals Teleosts: The large group of fish that have a not breeding with another such group and skeleton composed, at least in part, of which has the characteristics which distin- bone. guish it from other groups. Total length: A standard measurement of Stock: Term used in natural resource man- fish length from the tip of the snout to the agement as the group of individuals of a tip of the tail. Most commonly used for species that can be managed as one unit. species with non-forked tails. The number of stocks of a species depends on movement and breeding Transect: An imaginary line drawn through within the populations. an ecosystem in order to help ecologists sample and describe a biological commu- Strain: A genetically distinct group of indi- nity. viduals which may occur in a range of populations. They have a particular pro- Trophic level: The level of the food chain portion of alleles and may be referred to from which organisms obtain their energy. as a halotype if genetic analyses are per- Herbivores represent one level as plant formed. They show little genetic variation eaters. Carnivores represent another level and may be a result of a breeding line. as animal eaters.

Stratum: A horizontal layer of any material, Trichopterans: Caddis flies. especially a layer of sedimentary rock, usually one of several parallel layers (plu- Turbid: Not clear or transparent — water ral is strata). muddy with suspended silt or sediment.

Str eam: A small river. First-order streams Turbidity: A measure of the amount of sus- have no tributaries, second-order streams pended solids (usually fine clay or silt par- are formed by the confluence (flowing ticles) in water and thus of the degree of together of two streams) of two first-order scattering or absorption of light in the streams, third-order streams from the con- water; level of cloudiness in the water. fluence of two second-order streams, etc. Upwelling: The vertical movement of water Substrate: The solid bottom of a water body from the bottom of a lake or ocean to the to which an animal may be attached, on surface. Upwellings often bring nutrient- which it moves about or with which it is rich water to the surface and cause otherwise associated. localised zones of high productivity.

Surimi: Reconstituted fish flesh. Watershed: : A boundary between areas drained by different river systems. Swamp: An area of soft, permanently or intermittently wet ground, often with Waterbody: Any water habitat, ocean, lake, coarse grasses or reeds. Also called a steam, wetland. marsh or wetland. Water table: The top level of water in the Taxon: A unit of biological classification, ground that occupies spaces in rock or such as species, genus or class; a group of soil and lies above a layer of impermeable organisms sharing common characteristics (non-porous) rock. (plural taxa).

216 Bureau of Rural Sciences Weir: A barrier across a watercourse which may be submerged by rising water levels. Usually lower in height and built on smaller rivers than a dam.

Wetland: Any habitat that is permanently or intermittently covered by fresh water or saline water to a depth of up to 6 metres at low tide. Includes permanent rivers, intermittent streams, floodplains, lakes, billabongs, marshes, swamps and springs.

Zooplankton: The animal constituent of the plankton, small floating herbivores that feed on phytoplankton; a collective term for non-photosynthetic plankton.

Zostera: Generic name for eelgrass or long sea grass; grows in estuaries and bays.

Managing the Impacts of Carp 217

Scientific names

Fish

Atlantic salmon Salmo salar Australian bass Macquaria novemaculeata Australian grayling Prototroctes maraena Australian smelt Retropinna semoni Barramundi Lates calcarifer Basses Percichthyidae Big-headed carp Aristichthys nobilis Black br eam Acanthorpagrus butcheri Black carp Mylopharyngodon piceus Bony herring Nematalosa erebi Bream Albamis brama Brown tr out Salmo trutta Carp (includes mirror, leather, king, scaled and European carp) Cyprinus carpio Checkon Pelecus cultratus Chub Leuciscus cephalus Cods Percichthyidae Colarado squawfish Ptychocheilus lucius Congolli Pseudaphritis urvilli Crucian carp Carassius carassius Dace Leuciscus leuciscus Darling river har dyhead Craterocephalus amniculus Dwar f galaxias Galaxiella pusilla Eels Anguillidae Estuary per ch Macquaria colonorum European barbel Barbus barbus Fat-headed minnows Pimephales promelas Flathead gudgeon Philypnodon grandiceps Fork-tailed catfish Arius graeffei Freshwater catfish Tandanus tandanus Gambusia Gambusia holbrooki Galaxiids Galaxiidae Gemfish Rexea solandri

Managing the Impacts of Carp 219 Golden galaxias Galaxias auratus Golden per ch Macquaria ambigua Goldfish Carassius auratus Grass carp Ctenopharyngodon idella Grunters Haemulonidae Gudgeons Eleotridae Guppies Poecilia reticulata Hardyheads Atherinidae Jungle per ch Kuhlia rupestri Long-finned eel Anguilla reinhardtii Macquarie per ch Macquaria australasica Mangr ove jack Lutjanus argentimaculatus Minnows Galaxiidae Mountain galaxias Galaxias olidus Mud carp Cirrhinus molitorella Mullets Mugilidae Murray cod Maccullochella peelii peelii Murray galaxias Galaxias rostratus Murray har dyhead Craterocephalus fluviatilis Non-parasitic lampr ey Mordacia praecox Norther n cod Gadus morhua Ox-eye herring Megalops cypdnoides Oxelyan pygmy per ch Nannoperca oxleyana Per chlets Kuhliidae Pike Esox lucius Prussian carp Carassius carassius Rainbr ow tr out Oncorhynchus mykiss Rainbowfish Melanotaeniidae Redfin per ch Perca fluviatilis Redtail black ‘shark’ Puntius spp. River blackfish Gadopsis marmoratus Roach Rutilus rutilus Rosy barb Puntius conchonius Rudd Scardinius erythrophthalmus Saratoga Scleropages leichardti Shiners Notropis spp.

220 Bureau of Rural Sciences Short-finned eel Anguilla australis Silver carp Hypophthalmichthys molitrix Silver per ch Bidyanus bidyanus Souther n bluefin tuna Thunnus maccoyii Souther n purple spotted gudgeon Mogurnda adspersa Souther n pygmy per ch Nannoperca australis Spangled per ch Leiopotherapon unicolor Swor d tails Xiphophorus helleri Tench Tinca tinca Tilapia Oreochromis spp. Trout cod Maccullochella macquariensis Variegated pygmy per ch Nannoperca variegata Wester n carp gudgeon Hypseleotris klunzingeri White br eam Blicca bjoerkna Yarra pygmy per ch Nannoperca obscura

Mammal

Water rats Hydromys chrysogaster

Birds

Cor morants Pelecanidae Pelican Pelicanus conspicillatus

Reptiles

Estaurine cr ocodile Crocodylus porosus Freshwater cr ocodile Crocodylus johnstoni

Invertebrates

Daphnia Daphnia spp. Midges Chironomidae Yabbies Cherax destructor

Managing the Impacts of Carp 221 Plants

Attached algae Chara sp. Bluegr een algae Cyanobacteria Common water milfoil Myriophyllum papillosum Derris r oot Derris spp. Filamentous algae Spirogyra sp. Juncus Juncus spp. Plant-like algae Chara sp. Phragmites Phragmites australis Pondweed Potomogeton spp. Poplars Populus spp. Ribbonweed Vallisneria sp. River r ed gum Eucalyptus camaldulensis Soft-stemmed pondweed Potamogeton pectinatus Typha Typha spp. Willows Salix spp.

Agents causing diseases

Anchor wor m (crustacean) Lernaea cyprinacea Asian fish tapewor m Bothriocephalus acheilognathi Blood fluke (digenea) Sanguinicola inermis Car nation-head tapewor m (cestode) Caryophyllaeus laticeps Cheilodonelliasis (protozoa) Cheilodonella cyprini, Cheilodonella hexastichus Cottonwool fungus Saprolegnia Disease caused by (protozoa) Apiosoma piscicola Disease caused by (protozoa) Ichthyobodo necator Disease caused by (monogenea) Gyrodactylus sp. Disease caused by (protozoa) Myxosoma dujadini, Myxosoma encephalica Disease caused by (digenea) Neodiplostomum perlatum Emphysematous putr efaction (bacteria) Edwardsiella tarda Enteritis (protozoa) Eimeria cyprini, Eimeria subepithelialis Exter nal gill parasite (monogenea) Dactylogyrus anchoratus, Dactylogyrus vastator Gill r ot (fungus) Branchiomyces sanguini Goldfish ulcer disease (bacteria) Aeromonas salmonicida Gut flukes (digenea) Allocreadium isosporum, Allocreadium carporum

222 Bureau of Rural Sciences Kidney disease (protozoa) Sphaerospora cyprini Spring V iraemia of Carp V irus Rhabdovirus carpio Tissue parasite (protozoa) Myxobolus muelleri Trichodiniasis (protozoa) Trichodinella sp., Trichodina domerguei Weakness disease (protozoa) Cryptobia cyprini Whitespot (protozoa) Ichthyophthirius multifilis

Managing the Impacts of Carp 223

Index

A grazers, 55, 63 abundance of carp, 9, 24, 29, 30, 31, 38, 40, growth, 53 41, 43, 48, 53, 54, 55, 58, 59, 64, 66, 67, recurrent blooms, 127 84, 85, 87, 95, 111, 113, 115, 116, 117, turbidity, 120 121, 129, 133, 145, 153, 154, 158, 164, 177 Allocreadium isosporum, Allocreadium car- accidental release, 26, 141, 142, 177 porum live fish as bait, 26 see gut flukes action groups for carp, 74 altered flow, 38, 75, 123 Acts altered habitat, 29 Biological Control Act 1984, 127 altitude, 31, 37, 43 Fisheries Act 167, 100 see also high elevations Fisheries Act 1958, 23, 102 ammonia concentrations, 82 Fisheries Act 1982, 100, 106 amphibians, 125, 179 Fisheries Act 1994, 100, 109 anabranches, 24, 29, 52, 124 Fisheries Act 1995, 100, 103, 107 anal fin, 34 Fisheries Management Act 1994, 100, 104 analytical tools, 154 Fishing Act 1967, 107 anchor worm, 51 Flora and Fauna Guarantee Act 1988, angling, 14, 15, 48, 53, 62, 63, 66, 68, 70, 71, 103 72, 73, 74, 78, 101, 103, 107, 112, 113, Noxious Fish Act 1962, 102 116, 122, 140, 142, 154, 165, 206 Wildlife Protection Act 1982, 99, 100 catches, 112, 113, 140 adaptive experimental management, 8, 164 clubs, 66, 70, 72, 73, 74 see also experimental design Anguilla australis Aeromonas salmonicida see short-finned eel see goldfish ulcer disease Anguilla reinhardtii Africa, 11 see long-finned eel age, 11, 41, 45, 46, 47, 59, 95, 121, 177 Anguillidae structure, 121, 177 see eels aggregations of carp, 109 animal agricultural and urban development, 38 liberation, 68 agriculture, 7, 8, 9, 26, 27, 28, 38, 62, 66, 75, rights, 68 78, 102, 104, 109, 124, 133, 143, 148 welfare, 68, 150 Albamis brama cruelty, 68, 73 see bream annual growth patterns, 45 Albert River, 31 antigen, 129 Albury, 120 Apiosoma piscicola, 51 algae, 28, 40, 55, 61, 63, 83, 84, 85, 86, 126, aquaculture, 12, 14, 15, 23, 58, 70, 71, 89, 92, 127 101, 102, 116 algal aquaculturist, 61 blooms, 28, 48, 53, 54, 55, 62, 63, 83, 87 fishery, 12

Managing the Impacts of Carp 225 ornamental, 13 Australian Federation of Coarse Anglers aquaria, 40 Association (AFCAA), 73, 103 culture, 12 Australian Field and Game Associations, 66, 156 fish, 26 Australian Gourmet Imports, 92 Aquarium Society of New South Wales, 19 Australian grayling, 56, 58 aquatic Australian Quarantine and Inspection ecosystems, 19, 53, 55, 60, 79, 84, 85, 123, Service (AQIS), 92, 96 124, 179 Australian Recreational and Sport Fishing habitats, 29, 56, 63, 65, 71, 72, 80, 82, 87, Confederation (ARSFC), 71 101, 125, 143, 169, 174, 177, 178, 179 Australian salmon, 71 invertebrates, 27, 28 Australian smelt, 53, 54, 58 plants, 27, 28, 41, 55, 75, 79, 81, 85, 87, 94, 120, 124, 127, 138, 152, 156 Australian Society for Fish Biology (ASFB), 66 systems, 75, 118 Australian Water Technologies, 105 vegetation, 41, 58, 66, 84, 85, 106, 118, 140, 147, 153, 156, 162 B weeds, 13 backwaters, 29, 37, 40, 86 Aral Sea, 38 bacteria, 28, 87, 91 Aristichthys nobilis bag limit, 102, 106, 107, 112 see big-headed carp Bairnsdale, 128 Arius graeffei Baltic Sea, 15 see fork-tailed catfish banding patterns, 45 artificial lakes, 30, 32 Bangladesh, 92 Asia, 11, 12, 13, 18, 20, 21, 74, 87, 88, 89, 92, bank 96 collapse, 64 asian fish tapeworm, 51, 87 erosion, 27, 28, 63, 75, 80, 87, 117, 121, Atherinidae 138 see hardyheads slumping, 78 Atlantic salmon, 19 stability, 64, 65 attached algae, 84, 85 barbels, 16, 34, 35 attitudes to carp 7, 61, 62, 64, 68, 69, 70, 72, barrages, 31, 38, 69 73, 74, 78, 173 barramundi, 58 see also perceptions Barren Box Swamp, 42 Australian Abalone Exports Pty Ltd, 92 barriers to movement, 27, 31, 108, 130, 131, Australian bass, 53, 58, 112, 113 142, 144, 157, 159 ,160, 162, 173 Australian Capital Territory, 21, 32, 54, 73, bass, 55 102, 107, 128 Basscatch events, 112 carp management, 107 bed contours, 124 distribution of carp, 32 Before-After-Control-Impact (BACI), 120 introduction of carp, 20 benthivorous, 84 legislation, 100, 107 benthos, 83, 86, 87 Australian Code of Electrofishing Practice, 116 best guess estimates, 205 Australian Conservation Foundation (ACF), Bidyanus bidyanus 65, 66 see silver perch

226 Bureau of Rural Sciences big-headed carp, 14, 15 breeding patterns, 68 billabongs, 24, 27, 29, 37, 40, 45, 52, 59, 82, Branchiomyces sanguini 85, 87, 95, 118, 120, 121, 151, 157 see gill rot biodiversity, 8, 67, 150, 206 Britain, 61, 70 biofilms, 53 Broken River, 42, 43, 83 biological controls, 67, 151 brown trout, 19, 28, 65, 125 artificially enhanced pathogens, 129 buffer strips, 27 hormonal treatment, 130 Bureau of Rural Sciences (BRS), 7, 8, 9, 169, sterile ferals, 130 171 transgenic manipulation, 130 burley, 73, 74 biology, 7, 8, 60, 125, 126, 129, 130, 176, 177, Burrinjuck dam, 24 182 business plans, 101 biomanipulation, 8, 127, 128, 180 by-catch, 176, 182 biomass densities, 12, 24, 44, 55, 82, 84, 85, 86, 87, 94, 103, 112, 121, 122, 146 C biotechnology, 8, 129, 130, 143, 144 cages, 17, 84, 86, 146 birds, 48, 53, 67, 81, 84, 142, 143, 156, 179 campaigns, 68, 109, 142, 143, 144, 152, 182 black bream, 91, 93 Campaspe River, 42, 43 black carp, 11, 12, 13, 14 Canada, 82, 85, 121 Black Sea, 92 Canning River, 31 Blackwood River, 32 capture, 39, 67, 69, 73, 88, 103, 121, 122 Blicca bjoerkna capture and removal, 121 see White bream methods, 88 blood fluke, 51 Carassius auratus bluegreen algae, 28, 62, 75 see goldfish body size, 35, 55 Carassius carassius bodyweight, 35, 41, 45, 55, 73, 82, 84, 85, 92, see crucian carp, Prussian carp 103, 105, 112, 162 carnation-head tapeworm, 51 Bogan River, 55, 118, 135 carp bones, 45 as a scapegoat, 62, 64, 75 bony herring, 58, 84, 157 as competitors, 54 Boolara as predators, 53 strain, 19, 20, 21, 23, 25, 26, 61 as prey, 53 Boolarra Fish Farms Proprietary Limited, 21, carp-kill program, 103 23 control, 48, 54, 60, 64, 65, 66, 68, 69, 75, Bothriocephalus acheilognathi 78, 95, 102, 104, 105, 120, 123, 124, 128, see asian fish tapeworm 134, 140, 144, 145, 150, 151, 152, 153, boundaries, 139, 151, 182 154, 155, 167, 170, 175, 176, 177, 178, 179, 180, 181, 182, 205, 206 jurisdictional, 139 fisheries, 26, 69, 93, 104, 105, 123, 176 socio-political, 151 larvae, 42, 43, 45, 48 bounties, 68, 104, 105, 122, 123 Carp Assessment and Reduction Program Bourke, 67, 135 (CARP), 104, 105 bream, 13, 14, 17, 86 breathing air, 38

Managing the Impacts of Carp 227 Carp Control Coordinating Group (CCCG), 9, Cheilodonelliasis, 50 60, 100, 101, 102, 105, 109, 139, 150, 164, Chekhon, 15 167, 168, 171, 176, 182, 183 chemicals, 39, 62, 65, 69, 125, 126, 180 Carp Production Incentive Scheme (CPIS), acrolein, 126, 134 104 antimycin, 126 Caryophyllaeus laticeps copper sulphate, 30, 126 see carnation-head tapeworm endosulfan, 126 Caspian Sea, 15, 38, 92 human deaths, 126 catch pollutants, 39 catch-and-release, 73, 78, 112 chlorine, 39 data, 112, 113 copper, 30, 39, 126 rates, 83, 112 herbicide 2,4-D, 39 Catchment Management Authorities (CMAs), 65, 161, 170, 171 organochlorine insecticide endrin, 39 catchments, 28, 30, 65, 83, 124, 128, 138, 141, rotenone, 107, 125, 126, 134, 180 174, 177, 182 selenium, 39 action groups, 75 synthetic pyrethroids, 39 Albert River, 31 toxaphone, 39 changes, 56 Cherax destructor clearing, 27, 28, 159 see yabbies bank erosion, 27, 28, 75, 87, 117, 121, China, 11, 12, 13, 14, 17, 18, 92 138 Chinese carp, 17, 92 sheep, 27 Chironomidae siltation, 27, 56, 124, 147 see larvae of midges Glenelg River, 30 chironomids, 28, 40, 86 Hunter, 30 Chowilla floodplain, 124 management, 29, 72, 74, 151, 169, 170 chromosomal manipulation, 129, 181 rehabilitation, 29 chub, 14, 73 Shoalhaven, 24, 30 Cirrhinus molitorella Snowy, 30 see mud carp Catch-Per-Unit-Effort (CPUE), 111, 112 cladocerans, 40 cattle, 27, 75, 78, 88, 91, 156, 159, 161 clearing vegetation, 38 feed, 88, 91 climate, 56, 177 caudal fin, 34 conditions, 140, 155 causal links, 56, 79, 84, 85, 146, 147 cluster approach, 173 Centre for the Analysis and Management of coarse Biological Invasions (CAMBI), 176 anglers, 26, 62, 66, 69, 73, 142 Ceratopogonidae, 87 angling, 13, 14, 72, 103 channel bank erosion, 80 fish, 73 channel clearing, 28 coastal Chara sp. lakes, 30, 31, 32 see attached algae rivers, 20, 30, 37, 38, 58, 112 Cheilodonella cyprini, Cheilodonella hexas- cod, 55 tichus codes of practice, 170 see Cheilodonelliasis

228 Bureau of Rural Sciences Colorado squawfish, 14 competition, 28, 54, 55, 56, 58, 66, 73, 83, 94, colonise, 18, 131 105, 112, 121 colour (colouration), 16, 17, 18, 19, 20, 35, for food, 54, 59 127 competitive, 38, 103, 131 commercial compliance, 108, 142, 154 carp fishery, 104 staff, 142 catch records, 113 concept plans, 101 catches, 17, 56, 57, 74, 83 congolli, 69 efficient transport, 94 connectivity, 37, 123, 124 exploitation, 68, 69, 88, 91, 99, 101, 103, between habitats, 124 169 lateral, 34, 35, 41, 52, 123 fisheries, 19, 59, 78, 79, 115, 144, 149, 169 longitudinal, 123 fishing, 29, 48, 69, 71, 72, 93, 95, 104, 105, conservation, 8, 12, 15, 56, 65, 66, 87, 92, 106, 113, 115, 121 102, 128, 138, 139, 140, 141, 145, 169, 170 harvesting, 7, 67, 71, 88, 94, 95, 102, 103, groups, 65, 66 105, 106, 107, 123, 144, 150, 153, 167, status of native fish species, 56 176, 181 value, 12, 65, 87, 138, 141, 145 licence holders, 69, 91, 165 conservationists, 65, 164, 179 operations, 69, 95, 107, 157 containment, 32, 108 statistics, 121, 154 Contingent valuation, 149 use, 7, 12, 17, 19, 29, 48, 56, 64, 67, 68, 69, 70, 71, 72, 74, 78, 79, 83, 88, 91, 93, 94, contraception, 45, 68 95, 99, 101, 102, 103, 104, 105, 106, 107, control of carp, 40, 54, 72, 101, 102, 123, 126, 109, 111, 113, 115, 121, 122, 123, 125, 128, 130, 178 127, 139, 141, 144, 145, 150, 153, 154, options, 42, 59, 68, 69, 71, 138, 140, 146, 167, 169, 170, 176, 178, 181, 206 150, 179, 181, 205, 206 viability, 69, 106, 122 sites, 120 wild harvesting, 12 strategies, 9, 68, 150 common carp, 11, 13, 16, 34, 3592 effectiveness, 40 Commonwealth agencies, 101, 169 see also management and control Commonwealth FishCare Program, 158 cooking carp, 107 community, 8, 60, 62, 63, 64, 67, 70, 75, 79, see also human consumption 86, 87, 99, 101, 102, 104, 105, 110, 133, Cooper Basin, 106 140, 142, 144, 152, 155, 156, 164, 167, 169, 170, 172, 173, 176, 182, 183 Cooper Creek, 126 awareness, 64, 100, 105 Cooperative Research Centre (CRC), 42, 43, 60, 129, 175, 176 cooperation, 64 Cooperative Research Centre education, 142 for the Biological Control of Pest Animals, groups, 157, 158, 159 129 rural communities, 62, 133 for Freshwater Ecology (CRCFE), 42, 60, see also public awareness 175, 176 Community Consultative Committee (CCC), Coorong lakes, 31, 91, 106 110 copepods, 40, 48, 87 compensation, 67, 127, 178 copper sulphate, 30, 126 compensation claims, 67 corixids, 40

Managing the Impacts of Carp 229 cormorants, 48, 53 dace, 14, 17, 73 cost of control, 134, 135 dairy industry, 109 monetary, 97, 155, 157, 158, 159, 164 damage cost-effective, 8, 89, 104, 126, 129, 139, 141, caused by carp, 65, 69, 70, 94, 95, 99, 102, 145, 151, 176, 178, 181 104, 138, 145, 150, 167, 175, 177, 179, Cotter River, 32 182, 205, 207 cottonwool fungus, 49 control thresholds, 95 Craterocephalus amniculus dams, 20, 24, 26, 27, 30, 32, 48, 56, 61, 93, 103, 106, 109, 118, 130, 131, 135, 151 see Darling river hardyhead Danube crayfish, 69, 91 Basin, 13 cray bait, 70, 90, 91 River, 12 industry, 69 Daphnia spp., 40 creeks, 12, 18, 26, 37, 43, 115 Darling River, 21, 24, 25, 43, 56, 67, 121 crisis management, 138 Darling River hardyhead, 56 criteria for fish spawning, 42 death of carp, 39 Crocodylus johnstoni decapods, 40 see freshwater crocodile decision analysis, 145, 150 Crocodylus porosus framework, 145 see estuarine crocodile defining the problem, 7, 10, 138, 139, 156, cross-breeding, 17 161, 164 Crucian carp, 12, 13, 16, 18, 31, 35 degradation, 35, 62, 64, 65, 66, 72, 75, 82, 84, Crustaceans, 39, 40 87, 99, 123, 179 Cryptobia cyprini deliberate see weakness disease introduction, 26, 142 Ctenopharyngodon idella release, 26, 142 see grass carp transfer of carp, 73, 142 Cudgewa Creek, 29 delivery methods, 180 cultural, 67, 150 density cultured carp, 40, 92 low, 44, 55, 94, 95, 143 Cyanobacteria see also abundance of carp see bluegreen algae Department of Agriculture, Fisheries and cyanobacterial bloom, 30 Forestry (AFFA), 100 Cyprinidae, 11 Department of Primary Industries (DPI), 21, Cyprininae, 16 100, 110 cyprinids, 11, 12, 18, 31, 34, 35, 73, 92, 127 Derris spp., 125 Cyprinus carpio desnagging, 28 see common carp, European carp, king detoxifying, 125 carp, leather carp, mirror carp detritus, 40, 86, 87 Czech Republic, 92 diagnostic characters of carp, 35 D diet, 17, 39, 40, 53, 54, 55, 59, 83, 86, 122, 146 Dactylogyrus anchoratus, Dactylogyrus vas- dietary overlap, 54, 83 tator, Gyrodactylus sp. digestion, 39, 177 see external gill parasite times, 39

230 Bureau of Rural Sciences discount rate, 148, 205 interactions, 39, 52 discounting, 143, 205 processes, 52, 87, 123, 129 diseases, 8, 26, 46, 48, 67, 81, 87, 99, 101, Ecologically Sustainable Development 107, 121, 127, 206 (ESD), 7 carp-borne disease, 81, 87 economic fungal, 87 commensurate reductions, 205, 206 notifiable, 127 financing, 205 parasites, 46, 48, 87 frameworks, 148, 149 dispersal, 124, 131 gain, 156, 157 distribution and abundance, 7, 29, 38, 60, impacts, 7, 9, 10, 69, 70, 71, 77, 78, 88, 94, 139, 164, 177 102, 103, 121, 129, 138, 139, 143, 145, distribution of carp, 20, 23, 25, 42, 58, 139, 150, 176, 178, 205 153, 164, 179 incremental marginal change, 205 see also range of carp interest rate, 205 disturbance, 26, 27, 37, 56, 58, 118, 120, 123, net present values, 205 124 tax incentives, 206 river flow, 37 ecosystem, 38, 52, 64, 65, 79, 80, 92, 120, environment, 37, 38 124, 134, 141, 152, 154, 176, 179 habitats, 29, 37 balance, 52 fine sediments, 38 components, 79, 120, 152 Doitsu, 17 education, 26, 100, 104, 107, 110, 142, 157, domestic, 78, 88, 91, 125 161, 168, 169, 171, 173, 176, 182 dominance, 37, 55, 92, 133 strategy for carp, 64 dorsal Edwardsiella tarda fin, 34, 35 see Emphysematous petrefaction spines, 88 eels, 19, 58 downstream kills, 126 Eimeria cyprini, Eimeria subepithelialis drainage, 26, 32, 180, 182 see enteritis drought, 24, 48, 155 eggs, 27, 41, 42, 45, 53, 81, 83, 108, 109, 128, 129, 141, 143, 181 dry years, 43 hatching, 41 drying, 59, 67, 88, 124, 134, 158 production, 42 cycles, 27, 29, 156, 157 electric seines, 117 phase, 29 electrofishing, 69, 96, 108, 116, 117, 134, 135, dwarf galaxias, 56, 84, 87 162, 206 E current, 116 earthworks, 108 duty cycle, 116 East Gippsland Coastal Board, 70 field, 116 East Gippsland Shire, 70 injuries, 116 East Gippsland Water, 97 output frequency, 116 ecological, 37, 39, 52, 54, 58, 59, 65, 68, 69, selectivity, 116 80, 87, 102, 103, 117, 123, 127, 129, 149, 151, 154, 164, 177 voltage, 116 balance, 68, 127 electrophoresis protein analysis, 20

Managing the Impacts of Carp 231 Eleotridae Eummerring Creek, 73 see gudgeons Eurasia, 15 emigration, 41, 44, 46, 128 Europe, 11, 12, 13, 14, 15, 17, 18, 20, 21, 23, energy trap, 55, 84 29, 38, 39, 45, 48, 61, 67, 73, 74, 78, 84, 88, 89, 92, 96, 104, 106, 124, 126, 127 Emphysematous petrefaction, 49 European carp, 13, 16 enteritis, 50 eutrophic, 14, 28, 63, 92 Environment ACT, 26, 32, 100, 102, 107 evaluation Environment Australia (EA), 8, 9, 99 see monitoring and evaluation Environment Protection Authority, 97 evidence, 7, 11, 18, 19, 21, 23, 43, 45, 53, 54, environmental, 9, 10, 26, 29, 59, 62, 66, 67, 56, 58, 64, 79, 83, 99, 101, 107, 121, 179 69, 74, 77, 80, 82, 88, 94, 99, 103, 104, 105, 118, 124, 126, 129, 133, 134, 143, equivocal, 155 145, 150, 169, 170, 173, 182, 207 exclusion, 7, 68, 84, 118, 128, 144, 146, 181 authorities, 64 barriers conditions, 41, 44, 45, 48, 54, 63, 122, acoustic, 181 152, 176 devices, 128, 157 factors, 48, 120 bubble curtains, 128 impacts, 7, 65, 79, 120, 127, 130, 178, 179 sonic barriers, 128 monitoring, 12, 15 zones, 118 rehabilitation, 7, 65, 68, 123, 179, 180 excreting nutrients, 55 tolerances, 37, 38, 54 excretory products, 120 variability, 48, 58, 120 exotic, 8, 23, 26, 28, 37, 66, 102, 106, 110, 127 variations, 44, 95 experimental design ephemeral floodplain habitats, 43 management actions, 145 epidemiological, 129 see also adaptive experimental design eradication of carp, 10, 18, 19, 23, 63, 64, 65, exploitation, 26, 27, 29, 54, 93, 96, 101, 106, 66, 67, 69, 70, 74, 78, 99, 101, 102, 103, 121, 128, 176 106, 107, 108, 110, 125, 126, 135, 139, competition, 54, 121 142, 143, 144, 150, 153, 162, 169, 179 export, 71, 74, 88, 89, 92, 144, 178 local, 7, 138, 143 industry, 71, 74 national, 143, 144 markets, 74, 89, 96, 178 time-limited campaign, 143 external gill parasite, 51 erosion, 27, 28, 62, 64, 75, 78, 80, 83, 117, 121, 138 extension services, 8, 169, 173 see also bank erosion, catchment clearing extinct, 37, 56 Esox lucius F see pike factorial experimental design, 147 estaurine crocodile, 58 Family Cyprinidae, 11, 12, 33 estaurine systems, 30, 31, 32 fancy carp, 17 estimating carp abundance Far West Anglers Association (FWAA), 71, 73 single mark–recapture, 117 farm dams, 19, 23, 30, 31, 79, 82, 102, 103, 107, 109, 126, 140, 144 sequential depletion method, 117 farming, 19, 21, 23, 26, 27, 30, 31, 48, 71, 79, estuary, 38, 58 82, 91, 92, 102, 103, 107, 109, 126, 127, estuary perch, 58 140, 144

232 Bureau of Rural Sciences fat-headed minnows, 15 Fisheries WA, 31, 71, 109 Fatality Gene (FG), 126, 130, 151, 181 fishing, 17, 32, 46, 48, 66, 69, 70, 73, 74, 78, Inducible Fatality Gene (IFG), 8, 130 79, 88, 91, 92, 95, 102, 103, 104, 105, 106, 107, 108, 109, 110, 112, 113, 115, 116, programmed fatality, 129, 130 121, 122, 135, 153, 173, 176 fauna, 11, 28, 30, 55, 56, 86, 87, 123, 146, 180 effort, 105, 112, 113, 115 fecundity, 121, 177, 181 tackle, 70 feeding off-take, 88 behaviour, 39, 54, 81, 82, 129 fishway, 52, 63, 69, 116, 130, 131, 133, 142 food capture methods, 39 Denil, 131, 132 habits, 12 monitors, 133 morphology, 53 rock-ramp, 131, 132, 133 mouth structure, 39 trap-and-truck, 131 feral, 7, 8, 88, 121, 129, 130 vertical-slot, 131, 132 fertilisation of eggs, 41, 81 flathead gudgeon, 87 fertilisers, 28, 69, 75, 88, 89, 91, 97 flocculants, 109 liquid fertiliser, 90, 91 floodplains, 27, 29, 37, 43, 48, 52, 54, 58, 83, fertility, 26, 45, 130 106, 115, 134, 151, 169 control techniques, 42 habitats, 37, 43, 52, 54, 58 Field and Game Associations, 159, 170 inundation, 43 filamentous algae, 85 floods, 24, 39, 43, 44, 48, 52, 54, 57, 95, 113, filleting carp, 88, 91 142, 143, 155, 156, 158 Finniss River, 31 flora, 103, 146, 180 fish flow biologists, 153 alteration, 56 communities, 27, 37, 55, 62, 133 cycle, 27 counters, 116 events, 133, 155 elevators, 131 modifications, 84 fish-eating birds, 48, 58 regime, 29, 37, 68, 124, 133 see also piscivorous birds regulation, 37 larvae, 43 flowing-water environments, 127 locks, 131 food oils, 88 availability, 40, 45 passages, 106 chain, 54, 55, 69, 84, 127, 180 pumps, 131 manipulations, 54 fisheries, 56, 66, 70, 73, 78, 84, 92, 99, 101, processing, 39 102, 106, 107, 109, 113, 115, 117, 125, production, 12, 45 126, 128, 153, 154, 167, 175, 176, 178, 182 supply, 46, 53, 86 Fisheries (Freshwater) Management Plan webs 1999, 109 aquatic, 55, 124 Fisheries Action Program, 60 ecology, 55 fisheries departments, 99 lakes, 55 Fisheries Research and Development Corporation (FRDC), 60, 169, 176 riverine, 55 Fisheries Victoria, 65, 70, 73, 103 forestry, 8, 27, 116

Managing the Impacts of Carp 233 fork-tailed catfish, 58 manipulations, 71 forum on carp, 66, 74, 126 reporter gene, 130 Fraser River (Canada), 38 strains, 12, 17, 18, 19, 20, 21, 25, 26, 35, 92 fraudulent practices, 123 see also Boolara, Prospect, Yanco, Koi freshes, 134 see also Fatality gene, immunocontracep- freshwater, 11, 19, 30, 31, 32, 38, 41, 42, 43, tion 45, 52, 54, 55, 56, 58, 66, 69, 70, 71, 78, Geographic Information Systems (GIS), 139 83, 87, 109, 125, 153, 170, 175 Germany, 17, 92, 102 catfish, 54, 55, 57, 58, 66, 69, 83 gill arch, 16, 34 crocodile, 58 gill rot, 49 fish, 19, 41, 55, 56, 58, 87, 109, 164 gills, 39, 125, 127 habitat, 38, 125 modified, 38 fruit flies, 87 Gippsland lakes, 20, 25, 30, 39, 62, 69, 93, G 121, 122, 159 Gadopsis marmoratus Gippsland Lakes and Catchment Action see river blackfish Group, 70, 73, 79 Gadus morhua Golden carp see northern cod see goldfish Galaxias auratus golden galaxias, 56 see golden galaxias golden perch, 29, 48, 52, 53, 54, 55, 56, 57, 58, 70, 83, 84, 87, 107, 124, 128, 180 Galaxias olidus goldfish, 12, 13, 16, 17, 18, 24, 26, 30, 31, 34, see mountain galaxias 35, 61, 87, 99, 101, 103, 109, 142 Galaxias rostratus goldfish ulcer disease, 49, 87, 49 see Murray Galaxias Gondwanaland, 11, 55 Galaxiella pusilla Googong Reservoir, 107 see dwarf galaxias Goulburn River, 25, 162 Galaxiidae government, 8, 9, 10, 148, 169 see galaxiids agencies, 8, 65, 72, 78, 99, 140, 144, 155, galaxiids, 58 159, 167, 169, 173 gambusia, 19, 38, 56, 65, 87, 109, 125 departments, 64, 170, 173 Gambusia holbrooki grass carp, 11, 12, 13, 126 see gambusia grass substratum, 41 game fish grazing, 53, 64, 84, 127 salmon, 17 groundwater systems, 105 trout, 17, 18, 26, 28, 32, 54, 56, 58, 65, 66, growth rates, 38, 40, 45, 46, 177 70, 78, 84, 92, 125 grunters, 55, 58 gastropods, 86 gudgeons, 15, 54, 55, 58 Gawler River, 31 guppies, 19 gemfish, 121 Gurra Lakes, 45 gender manipulation, 8, 129 gut flukes, 50 genetic, 20, 71, 92, 129, 130, 150, 151 gene pool, 92 genetically modified stocks, 71 genome, 130

234 Bureau of Rural Sciences H high flow events, 27, 37, 52 habitat, 26, 27, 29, 35, 37, 41, 42, 43, 47, 52, high-risk strategy, 126 56, 63, 65, 66, 67, 71, 72, 75, 80, 84, 86, Hong Kong, 13, 99 87, 95, 101, 115, 116, 117, 118, 120, 121, hook and line, 112 122, 123, 124, 125, 128, 131, 133, 134, 135, 139, 140, 141, 143, 146, 153, 155, human 169, 174, 177, 178, 179, 182, 205 disturbance, 58, 69 carp 37, 40, 122, 134, 153 translocation, 125 channel, 43 human consumption, 12, 69, 74, 78, 81, 88, disturbance, 26, 37, 38, 58, 121 89, 90, 92, 96 cattle, 27, 75, 78, 88, 91 carp dishes, 88 turbidity, 27, 39, 55, 72, 75, 79, 81, 82, recipes for cooking carp, 74 83, 85, 86, 87, 109, 116, 117, 120, 125, Hume dam, 17, 24, 26, 27, 28, 29, 30, 40, 41, 139, 140, 147, 178 42, 43, 45, 53, 54, 79, 86, 87, 99, 124, 131 diversity, 27 hybrid, 26, 34, 35, 116 ephemeral habitats, 54 hydroelectricity, 26, 32 freshwater habitat, 38, 125 hydrological patterns, 27 habitat modifiers, 52 Hydromys chrysogaster littoral, 124 see water rats manipulation, 8 hypothesis, 37, 53, 83, 134, 146, 147, 173 preferences, 54, 108, 124 Hypseleotris klunzingeri rehabilitation, 65, 66, 69 see western carp gudgeon requirements, 60 I restoration, 63, 64, 65, 124, 128 ice, 91, 92, 96 river habitats, 27, 56, 64, 65, 66, 77 Ichthyobodo necator, 50 space, 54, 56 Ichthyophthirius multifilis stream, 28 see whitespot structure, 37, 124 illegal activities, 26, 67, 71, 72, 73, 102, 106, haemorrhagic disease, 126 107, 109 Haemulonidae immigration, 40, 41, 44, 46, 122, 128, 143, 152 see grunters immunocontraception, 71, 129, 151 handling methods, 94 impacts of carp, 7, 8, 35, 39, 56, 57, 61, 63, 69, hardyheads, 55, 58 77, 78, 79, 80, 87, 102, 117, 118, 121, 131, harvesting of carp, 7, 29, 44, 66, 67, 68, 69, 134, 138, 140, 149, 153, 154, 155, 158, 168, 70, 71, 88, 89, 91, 93, 94, 95, 104, 106, 171, 172, 175, 178, 179 121, 122, 144, 150, 151, 169, 176, 178, 182 economic, 7, 78, 178 one-off, 95 environmental, 7, 65, 79, 120, 127, 130, Harvey River, 31 156, 178, 179 hatchery production, 23 industry, 78 hatchery-produced carp, 23 native fish, 8, 23, 24, 26, 27, 28, 29, 38, 48, Hawkesbury–Nepean River, 113 53, 54, 55, 56, 58, 61, 63, 64, 66, 67, 69, 71, Hazelwood Pondage, 73 72, 73, 75, 78, 80, 83, 84, 87, 121, 123, 124, 138, 157, 171, 172 Hedonic pricing, 149 potential, 102, 107, 110, 177 hemipterans, 86 sediment deposition, 120 high elevations, 30, 31 substrate pock marks, 120

Managing the Impacts of Carp 235 implementation, 7, 8, 9, 10, 29, 78, 123, 133, invasive, 56, 124, 176 138, 150, 152, 157, 162, 164, 167, 169, invertebrate food sources for fish, 27 170, 173, 176, 182, 205, 206 invertebrates, 28, 40, 54, 82, 86, 138 plan, 138, 170 investments, 67, 95, 96, 121, 149, 206 import, 17, 61, 89, 92, 99, 169 irrigation, 19, 26, 27, 28, 30, 31, 37, 41, 52, 62, live carp, 99 66, 67, 78, 79, 80, 85, 105, 121, 133, 134, restrictions, 169 139, 140, 178 impoundments, 24, 26, 30, 32, 54, 56, 124, channels, 19, 26, 30, 31, 78, 80, 121, 134, 128 139, 140 incentives, 69, 105, 123 J carp harvesting, 105, 123 Japan, 13, 17, 35, 92 financial, 122 Jewish kosher requirements, 92 increase in numbers, 67 Juncus spp., 42 incursions, 176 jungle perch, 58 index of carp numbers, 111 juvenile carp, 29, 37, 38, 42, 43, 44, 46, 47, India, 11, 92 48, 52, 53, 109, 112, 128, 131, 134, 140, 143, 159, 157, 161, 181 indices, 152, 153, 154 indigenous K K&C Fisheries, 69, 71, 74, 88, 91, 92, 93, 96, peoples, 67 97 communities, 67, 86, 150 kidney disease, 49 Indonesia, 40, 92 king carp, 18 Indo-West Pacific, 121 King River, 29 Inducible Fatality Gene (IFG), 8, 130 knowledge, 7, 8, 9, 35, 40, 58, 60, 62, 89, 94, Inducible Sterility Gene (ISG), 130 104, 125, 126, 145, 154, 173, 175, 178, 182 infertility, 45, 129 current, 138, 175 Inland Fisheries Commission (IFC), 38, 43, gaps, 9, 60, 148, 175 46, 79, 107, 124, 128 Koi, 13, 16, 17, 19, 20, 21, 26, 31, 32, 35, 70, insecticide, 125 71, 92, 103 insects, 28, 39, 40, 122 breeding, 17 aquatic, 40 varieties, 17 benthic, 40, 86 Koi aquaculture facility, 21 terrestrial, 27, 28, 40 Kuhlia rupestri intangibles, 205, 207 see jungle perch Integrated Monitoring of Environmental Kuhliidae Flows program, 29, 105 see perchlets interference competition, 54, 121 L interim management strategy, 102 laboratory conditions, 129 internet, 142, 183 Lachlan River, 25, 55, 69, 80, 85 introduced species, 37, 38, 54, 56, 62, 65, 66, Lake Alexandrina, 25, 31, 38, 40, 91 67, 70, 75, 91 Lake Burley Griffin, 20, 21, 54, 73, 107 fish, 61, 87, 103, 106, 109, 110, 125 Lake Crescent, 19, 20, 21, 25, 32, 45, 46, 107, cyprinids, 17 108, 109, 128 plants, 28 Lake Eyre, 25, 26 inundation, 29, 45, 134 Lake Ginninderra, 107

236 Bureau of Rural Sciences Lake Hawthorn, 19, 20, 23 locks, 69 Lake Sorell, 19, 25, 32, 107, 108, 109, 128 logistics, 138 Lake Victoria, 30 population growth curve, 44 Lake Wellington, 23, 30, 96 longevity, 17, 95, 130 lakes, 17, 18, 19, 21, 23, 24, 26, 30, 31, 32, 37, long-finned eel, 58 38, 39, 40, 41, 43, 45, 46, 54, 55, 56, 62, long-term, 9, 65, 66, 69, 102, 121, 123, 130, 69, 70, 73, 79, 83, 84, 85, 86, 91, 92, 93, 138, 139, 140, 144, 153, 154, 176, 177, 182 106, 107, 108, 109, 115, 121, 123, 124, data sets, 177 127, 128, 143, 144, 176, 181 monitoring, 154 Land and Water Resources Research and Development Corporation (LWRRDC), 60 low carp price, 88 land lowland rivers, 28, 37, 55 clearance, 27 Lutjanus argentimaculatus vertebrates, 88 see mangrove jack Landcare, 168, 170, 173 M landholders, 63, 64, 65, 80, 164, 170 Maccullochella macquariensis larvae of midges, 28, 40 see trout cod lateral line, 16, 34, 35 Macintyre River, 24, 31 Lates calcarifer Macloeds Morass, 159, 160 see Barramundi Macquaria ambigua leather carp, 13, 16, 17 see golden perch legal, 95, 127, 145, 150 Macquaria australasica legislation, 7, 100, 101, 102, 103, 107, 109, see Macquarie perch 110, 142, 167, 169 Macquaria colonorum Leigh Creek Retention Dam, 25, 126 see estuary perch Leiopotherapon unicolor Macquaria novemaculeata see spangled perch see Australian bass length of carp, 16, 34, 40, 46, 86 Macquarie perch, 56, 58, 70 Leptoceridae, 87 Macquarie River, 25 Lernaea cyprinacea macroinvertebrates, 29, 53, 80, 82, 83, 86, 87, see anchor worm 158, 162, 179 lethal limit, 38, 39 macrophytes, 27, 38, 63, 80, 82, 84, 85, 120, 146, 147, 158 Leuciscus cephalus Macullochella peelii peelii see chub see Murray cod levels of oxygen, 38 Ma-goi life cycle of carp, 29 see fancy carp Light River, 31 management and control Lindernow, 97 adaptive experimental approach, 8 Little Moe River, 25, 161, 162 biomanipulation, 8, 127, 128, 180 littoral vegetation, 29 biotechnology, 8, 129, 130 live fish as bait, 26 bounties, 68, 104, 105, 122, 123 livestock access, 63, 81, 147 chromosomal manipulation, 129, 181 lobby, 167 local markets, 74

Managing the Impacts of Carp 237 commercial harvesting, 7, 67, 71, 88, 94, sustained management, 7, 10, 96, 139, 95, 102, 103, 105, 106, 107, 123, 144, 150, 144, 157, 165, 181 153, 167, 176, 181 targeted, 10, 96, 139, 144, 162 commercial use, 7, 70, 88, 95, 101, 178 unit, 9, 138, 145, 150, 151 commercial wild harvesting, 12 zones, 182 control techniques, 8, 42, 60, 65, 66, 144, mangrove jack, 58 145, 150, 155, 169, 178, 181, 182, 206 maps, 138, 139 diet, 17, 39, 40, 53, 54, 83, 86, 122, 146 aerial photographs, 139 environmental rehabilitation, 7, 65, 68, topographic, 139 123, 179, 180 marginal analysis, 205, 206 eradication, 18, 23, 65, 66, 67, 69, 78, 102, 103, 106, 107, 108, 110, 125, 126, 135, Maribyrnong River, 73 139, 143, 144, 150, 153, 179 markets, 48, 69, 70, 71, 74, 88, 89, 91, 92, 93, exclusion, 7, 68, 84, 118, 128, 144, 146, 94, 95, 96, 103, 104, 106, 122, 126, 144, 157, 181 148, 149, 159, 170, 176, 178 feeding behaviour, 39, 54, 81, 129 Australian production, 93 gender manipulation, 8, 129 carp production levels, 93 genetic control technique, 71 competition from imported fish, 86 human consumption, 12, 69, 74, 78, 88, demand, 93 92 low prices, 71, 89, 92, 176 management options, 7, 65, 108, 124, markets for carp, 48, 93, 104, 106 139, 140, 141, 146, 150, 155, 177, 178, 205 potential harvest, 93 management plan, 7, 8, 9, 10, 102, 103, Marne River, 31 106, 139, 140, 145, 151, 154, 182 mathematical models, 130 developing, 7, 138, 139 matrices (pay-off), 206 molecular approaches, 7, 129, 181 maturity, 41, 44, 45, 105, 122, 128 national, 9, 99, 102, 138, 145, 167 age at maturity, 41 no management, 7, 138, 139, 145 maximum recruitment, 44 objectives, 139, 145, 152, 179 Melanotaeniidae one-off control, 70, 139, 144 see rainbowfish ownership, 152 Melbourne Botanical Gardens, 18 passive-adaptive, 145 Menindee Lakes, 30 performance indicators, 139, 151, 152, methodology, 101 154, 179 microcrustaceans, 40 planned management, 68 migration, 27, 41, 52, 55, 128, 131, 143, 177 poisoning, 7, 32, 71, 84, 106, 107, 125, 126, 134, 135, 144, 150, 157, 181 migratory behaviour, 52 precautionary management, 7, 10, 139, Millewa Forest, 42 141 Millmerran, 25 pre-management, 146 Ministerial Council of Forestry, Fisheries and recreational fishing, 7, 12, 17, 29, 70, 71, Aquaculture (MCFFA), 101, 102 72, 78, 79, 111, 121, 138, 139, 178 minnows, 14, 15 strategic management, 7, 8, 9, 138, 140, mirror carp, 13, 16, 17, 18 145, 152, 164 misconceptions, 62, 64 strategy, 8, 10, 59, 101, 139, 145, 146, 148, Mitchell River, 159 151, 152, 164 mobility, 52, 151

238 Bureau of Rural Sciences modified river flows, 58 Murray–Darling Association (MDA), 66, 157 Moe River, 162, 163 Murray–Darling Basin, 19, 20, 21, 24, 27, 28, Mogurnda adspersa 34, 46, 56, 57, 62, 101, 109, 124, 127, 134, 177 see southern purple spotted gudgeon Murray–Darling Basin Commission (MDBC), molecular approaches, 7, 129, 181 100, 101, 149, 156, 168, 171 molluscs, 39, 40 Murrumbidgee Catchment Management monitoring and evaluation, 7, 8, 10, 58, 59, Committee, 74 64, 97, 105, 113, 133, 138, 141, 142, 145, Murrumbidgee Irrigation Area (MIA), 19, 20, 152, 153, 154, 155, 158, 159, 163, 164, 41, 42, 134 165, 168, 169, 173, 176, 177, 179, 182, 205 Murrumbidgee River, 19, 24, 32, 41, 42, 47, misinterpreting information, 155 48, 52, 74, 134 operational monitoring, 8, 152, 182 Mylopharyngodon piceus performance indicators, 151, 152 see black carp performance monitoring, 8, 154, 155, 182 Myxobolus muelleri periodic, 153, 158 see tissue parasite repeat, 153 N Mordacia praecox Nannoperca australis see non-parasitic lamprey see southern pygmy perch mortality, 41, 42, 46, 47, 48, 59, 95, 127, 129 Nannoperca obscura eggs and larvae, 41 see Yarra pygmy perch fish mortality, 48 Nannoperca oxleyana high juvenile mortality, 42 see oxelyan pygmy perch high mortality rates, 65 Nannoperca variegata natural mortality, 48 see variegated pygmy perch rates, 41, 47 Narrandera, 21, 42 mountain galaxias, 28 national carp summits, 69, 72, 73, 101 movements, 52, 131, 142, 143 National Carp Task Force (NCTF), 31, 64, 69, mud carp, 11, 13 74, 101, 102, 167, 170, 183 muddiness National Feral Animal Control Program see water (NFACP), 7, 8, 9, 169 muddy surfaces, 41 national management guidelines, 9 Mugilidae National Management Strategy for Carp see minnows, mullets Control (NMSCC), 9, 60, 105, 109 mullets, 58 National Monitoring River Health Initiative, 29 multidisciplinary approach, 176 national strategic approach, 102, 164, 165, Murray cod, 24, 29, 48, 53, 54, 55, 56, 57, 58, 167, 171 64, 70, 83, 84, 87, 106, 107, 124, 128, 180, 206 native birds, 66 Murray galaxias, 56 native Murray hardyhead, 56 commercial fishery, 79 Murray–Darling 2001 FishRehab Program, 101, 171 Murray River, 19, 23, 24, 25, 27, 28, 29, 31, 32, 39, 40, 42, 45, 46, 47, 48, 52, 53, 56, 66, 67, 69, 86, 91, 93, 95, 106, 131, 156, 173

Managing the Impacts of Carp 239 fish, 8, 23, 24, 26, 27, 28, 29, 38, 48, 53, introduction of carp, 18, 20 54, 55, 56, 57, 58, 59, 61, 63, 64, 65, 66, legislation, 100 67, 69, 70, 71, 72, 73, 75, 78, 80, 83, 84, New South Wales Acclimatisation Society, 18 87, 91, 106, 116, 121, 123, 124, 125, 128, 131, 133, 138, 139, 142, 143, 149, 153, New South Wales Aquarium Society of New 159, 161, 162, 169, 170, 173, 176, 178, South Wales, 19 179, 180 New South Wales Department of Land and decline of, 29, 56, 57, 66, 67, 69, 75, 84, Water Conservation, 74, 104, 106 121 New South Wales Department of State and species, 35, 37, 52, 60, 79, 105, 107, 206 Regional Development, 104 Native Fish Australia (NFA), 66, 73, 170, 172 New South Wales Fisheries, 59, 100 native vegetation, 28, 59, 64, 149, 158 New South Wales Inland Commercial Fishery, 105 natural disturbance, 37 New South Wales National Parks and Natural Heritage Trust (NHT), 7, 9, 60, 101, Wildlife Service, 104 158, 159, 167, 168, 169 New South Wales Recreational Fishing for Water, the Environment and Fish (Freshwater) Licence, 106 Management, 101 New South Wales River Survey, 29 see Murray–Darling 2001 FishRehab Program New South Wales Water Reform Process, 29, 105, 10 natural lakes, 30 New South Wales Weirs Policy, 105 natural resource agencies, 175 niches, 54 naturalists, 170 nil-treatment, 145 Nematalosa erebi non-exclusion zones, 118 see bony herring non-indigenous fish, 102 Neodiplostomum perlatum, 51 non-parasitic lamprey, 56 Nephelometric Turbidity Units (NTU), 82, 83, 86, 120, 139 non-target native species, 67 nets, 69, 88, 91, 95, 108, 112, 113, 116, 117, non-target species, 68, 91, 107, 129, 150, 181 118, 134, 146, 205 North America, 11, 12, 15, 23, 39, 61, 126 cone trap, 113 northern cod, 121 drum, 112, 113 Notropis spp. fyke, 113 see shiners gill, 112, 113 noxious, 23, 71, 74, 100, 102, 103, 104, 107, keep, 107 109 mesh, 91, 113 null hypothesis, 146, 147 seine, 69, 91, 95, 96, 97, 113, 117 nursery networks, 26, 64, 70, 167, 173, 174 areas, 43 New Guinea, 11 habitats, 43, 134, 140 New South Wales, 18, 19, 20, 24, 26, 27, 29, nutrient, 82, 156, 172 30, 31, 37, 41, 42, 43, 44, 46, 53, 56, 57, concentrations, 78, 80 60, 62, 63, 64, 66, 67, 69, 70, 71, 73, 82, enrichment, 38, 56 83, 85, 87, 91, 93, 95, 102, 104, 105, 106, load, 28, 63, 86, 87 107, 113, 115, 123, 128, 134, 135, 170, 172, 173, 175 transfer, 55 carp management, 104, 105, 106 distribution of carp, 30, 31

240 Bureau of Rural Sciences O see Chekhon objectives, 7, 65, 94, 101, 102, 104, 134, 139, pelicans, 48, 53, 84 140, 151, 152, 153, 154, 155, 179, 182, 183 Pelicanus conspicillatus pre-determined, 154 see pelicans obstacles, 124 Perca fluviatilis oligochaetes, 86 see redfin perch omnivores, 40 perceptions, 7, 62, 70, 74, 75, 79, 81, 83, 88, Oncorhynchus mykiss 89, 126, 140, 164, 171, 181 see rainbow trout perchlets, 58 on-ground operators, 153 Percichthyidae Onkaparinga River, 25, 26 see bass, cod, 55, 70 operational monitoring, 8, 152, 182 performance opercular bones, 45 indicators, 151, 152, 158, 162, 165 operculum, 34 monitoring, 8, 154, 155, 182 opportunistic, 37, 43, 58, 99 permits, 66, 103, 105, 178 oral bait, 125 pests, 7, 8, 9, 23, 54, 65, 68, 70, 71, 80, 88, 99, Order Cypriniformes, 33 101, 102, 103, 105, 109, 110, 122, 123, 129, 135, 139, 143, 144, 145, 149, 150, Oreochromis spp. 152, 154, 167, 169, 179, 181, 182, 205, 206 see tilapia pet food, 71, 88 organisms, 26, 48, 55, 126, 129, 150, 151 pH, 39, 162 ornamental carp, 18, 35, 142 lethal limit, 38, 39 ornamental fish, 18, 70, 92, 99, 127 pharyngeal teeth, 33, 34, 35, 39, 53 ostracods, 40 Philypnodon grandiceps otoliths, 34, 45 see flathead gudgeon outlay, 143 phosphorus, 28, 63, 82, 83, 120 Ovens River, 42, 64 Phoxinus phoxinus overall ranking, 150 see minnows ox-eye herring, 58 Phragmites, 159 oxelyan pygmy perch, 56 physical exclusion, 84 oxygen concentrations, 37 physiology, 126, 177 see also algal blooms phytoplankton oxygen tolerances, 38 blooms, 82, 83, 87 P concentrations, 80 Paddys River, 32 pike, 61, 127 Papua New Guinea, 58, 177 Pilby Creek, 66, 71, 106, 128, 146, 156, 157, Paroo River, 24, 42, 43, 47, 48, 52 159, 160 particles, 37, 39, 120 pilchards, 71 clay, 83, 125 Pimephales promelas pathogens, 87 see fat-headed minnows pectoral fin, 34 piscicides, 117 Pelecanidae piscivorous see cormorants birds, 53 Pelecus cultratus

Managing the Impacts of Carp 241 fish, 48, 53 population, 12, 18, 19, 21, 23, 26, 28, 29, 30, native species, 55 31, 32, 37, 38, 43, 48, 53, 54, 55, 56, 58, 59, 62, 64, 66, 69, 71, 78, 81, 83, 84, 85, planktonic food, 52 88, 99, 102, 103, 104, 105, 106, 107, 108, plant material, 39, 40, 41, 122 109, 112, 113, 115, 117, 118, 120, 123, plants, 17, 27, 28, 29, 41, 55, 61, 84, 85, 125, 124, 125, 127, 128, 131, 138, 139, 140, 127, 152 141, 143, 144, 151, 153, 154, 155, 161, Poecilia reticulata 165, 169, 173, 180, 181 see guppies control, 45, 65, 67, 68, 95, 121, 126, 176, 179 poisons, 7, 23, 32, 71, 84, 106, 107, 125, 126, 134, 135, 144, 150, 165, 180, 181 dynamics, 8, 40, 41, 60, 95, 122, 129, 130, 177 community resistance, 144 genetics, 60, 130 rotenone, 107, 125, 126, 134, 180 growth, 24, 42, 44, 129 species specific, 125 increases, 44, 152 Poland, 74, 92, 96 management, 111 political, 143, 151 parameters, 41, 95 pollution simulation analysis, 44 bluegreen algae, 28, 62, 75 survey, 93 dairy farms, 28 Populus spp. detergents, 28 see poplars eutrophication, 28, 63 post-harvest fertilisers, 28, 75, 88 efficient transport, 94 fish kills, 28, 117, 126, 154 flesh quality, 91 industrial effluent, 28 handling, 90, 96 nutrients, 28, 29, 55, 75, 83, 120 ice preservation, 91, 92, 96 pesticides, 28, 125 Potamogeton pectinatus residues, 28 see soft-stemmed pondweed sewage, 28 potassium permanganate, 125 storm water, 28 Potentially Threatening Process, 103 thermal, 123 Potomogeton spp. toxic, 123 see pondweed viral counts, 28 precautionary management, 7, 139, 141 water, 74 predation, 28, 46, 48, 53, 54, 55, 58, 65, 66, see also chemical pollutants, algal 86, 121, 124, 128, 131, 180 blooms predators, 8, 15, 28, 46, 48, 52, 53, 55, 58, 61, polyculture, 12, 13, 14, 92 68, 84, 127, 128, 180, 181 pond culture, 17 populations, 53, 180 ponds, 12, 17, 18, 32, 40, 41, 52, 58, 79, 82, stockings, 8, 54, 68, 151, 181 85, 86, 92, 111, 118, 121, 127, 140 predatory native fish, 53, 106, 128 experiments, 41, 79 pre-fished levels, 122 pondweed, 85 pre-impact conditions, 120 poplars, 28 Prentiss Incorporated, 126 prey, 28, 39, 40, 52, 53, 54, 84 species, 40, 53

242 Bureau of Rural Sciences pricing, 71, 74, 88, 90, 91, 95, 105 Queensland Fisheries, 110 Primary Industries and Resources South Queensland Fisheries Management Australia (PIRSA), 106 Authority (QFMA), 100, 110 priority, 9, 35, 64, 65, 66, 95, 106, 138, 141, R 145, 150, 176, 178, 206 rabbit calicivirus, 127 setting, 145, 150 radiotracking, 52, 108 private raffia mats, 41 agencies, 152 rainbow trout, 19, 53, 65, 125 land, 167, 169 rainbowfish, 54, 58 waters, 23, 102, 103 range of carp processing techniques, 104 current, 138, 164 production of carp, 71, 92, 93, 95, 104 potential, 138, 141 profit, 69, 127, 206 see also distribution of carp prohibition, 23, 102, 109 recaptures, 52 Proposed Fisheries Regulation, 103 RecFish, 71, 72 Prospect Reservoir, 18, 20, 21, 25, 61 recipes, 74, 88, 173 Prospect strain, 19, 20, 21 recolonisation, 95, 124, 135, 140, 157, 158, Prototroctes maraena 162 see Australian grayling recovery studies, 120 Prussian carp, 13, 18 recreational Pseudaphritis urvilli carp fishery, 104 see congolli fishing, 7, 12, 17, 29, 48, 53, 62, 66, 68, 69, Ptychocheilus lucius 70, 71, 72, 73, 74, 78, 79, 92, 101, 103, 104, 105, 106, 107, 109, 111, 112, 113, see Colorado squawfish 115, 116, 121, 122, 128, 138, 139, 140, public 150, 154, 157, 176, 178, 206 authorities, 170 anglers, 17, 24, 26, 48, 54, 61, 62, 66, 70, awareness, 64 71, 72, 73, 78, 79, 112, 122, 142, 143, 172, concerns, 138, 156, 164 177, 205 interest, 99 fishing competitions, 64, 66, 70, 73, 74, 102, 103, 105, 107, 110, 112, 153, 154, pressure, 99 168, 172, 173 Puntius sp. prizes, 73, 110 see Redtail black ‘shark’ Recreational Anglers Association (RAA), 71 Q coarse angling, 26, 62, 66, 69, 73, 103, 142 Quality Assurance Program (QAP), 95 recruitment of carp, 38, 40, 41, 42, 43, 44, 45, quantitative, 86, 143, 154, 177 46, 53, 84, 95, 122, 127, 128, 159, 177 assessment, 154 rates, 41, 95 Queanbeyan River, 32 success, 43, 44 Queensland, 12, 18, 19, 21, 24, 29, 31, 52, 60, zones for carp, 43 95, 102, 109, 110, 128 redfin perch, 19, 27, 28, 48, 53, 65, 70, 87, carp management, 110 109, 125 introduction of carp, 19 Redtail black ‘shark’, 13 legislation, 100, 109 Reedy Lake, 159 Queensland Department of Natural refuges, 27, 28, 52 Resources, 24, 31 regional institutes, 175

Managing the Impacts of Carp 243 regulation of river flows, 52 rivers, 11, 19, 21, 24, 27, 28, 29, 30, 31, 32, 37, rehabilitation, 35, 65, 66, 138, 158, 161, 164, 38, 39, 40, 41, 42, 43, 44, 46, 47, 48, 55, 179, 180 56, 58, 63, 64, 66, 69, 79, 81, 83, 84, 85, 91, 92, 95, 105, 106, 118, 121, 122, 123, reintroduction, 107, 108, 124, 125, 126, 143, 124, 128, 131, 133, 134, 135, 143 144, 153, 158, 162 environments reinvasion, 135, 151 erratic and unpredictable, 55 relative abundance, 24, 111, 115 frontage, 27, 78 repeat spawning, 41, 42 health, 62, 75, 105 replication, 145, 146 management, 64, 65, 124 Report of the State Development Committee, 23 regulation, 75 reproduction, 41, 42, 44, 59, 95, 116, 122, riverbanks undermining, 62, 64, 65 129, 143, 177 systems, 17, 24, 43, 52, 80, 83, 99, 116, eggs, 27, 41, 42, 45, 53, 83, 108, 109, 128, 123, 134, 144, 151 129, 141, 143, 181 traffic, 27, 69 reptiles, 179 roach, 12, 14, 16, 17, 18, 73, 87 re-release of carp, 66 rock lobster industry, 91, 96 research on carp, 9, 40, 58, 59, 60, 64, 69, 71, Rocklands reservoir, 30 77, 80, 82, 84, 85, 86, 87, 96, 101, 102, rod limit, 107 104, 113, 118, 120, 121, 145, 146, 147, rosy barb, 12, 13 154, 155, 156, 157, 158, 159, 164, 168, 169, 175, 176, 179, 180, 181, 183 rotenone, 107, 125, 126, 134, 180 exclosure experiments, 84 see also poisons, chemical pollutants see also scientific evidence rudd, 14, 73 reservoirs, 18, 26, 37, 92, 126 S restocking, 12 safety, 126, 130, 135, 145, 150, 152 restoration, 63, 69, 161 saline waters, 28 Retropinna semoni salinity, 27, 30, 37, 38, 39, 62, 63, 81, 96 see Australian smelt Salix spp. Rexea solandri see willows see gemfish Salmo salar Rhabdovirus carpio see Atlantic salmon see Spring Viraemia of Carp Virus Salmonidae ribbonweed, 85, 158 see salmonids riparian vegetation, 27, 28, 63, 64, 72, 81, salmonids, 73, 92 123, 124, 146, 147, 156, 159, 161, 162, 171 sampling, 29, 31, 40, 44, 115, 117, 118, 134, fringing vegetation, 29 153 shading, 27, 28 biased, 153 River Basin Management Society sand, 40 Incorporated, 75 Sanguinicola inermis river blackfish, 28, 58, 63, 87, 161, 162, 163 see blood fluke River Management Committees, 154, 170 Saprolegnia River Management Trusts, 154 see cottonwool fungus river red gum, 41 saratoga, 58 riverine habitats, 23, 37, 43, 128 scaled carp, 13

244 Bureau of Rural Sciences scaleless, 17 size distribution, 113, 115 scales, 18, 33, 34, 35, 45, 85, 139, 151, 179 size limit, 112 Scardinius erythrophthalmus snags, 28, 64, 84, 96 see rudd desnagging, 28 schools, 53, 84, 113, 159, 163, 168, 170, 172, snails 173 see molluscs curriculum, 173 Snowy River, 30 scientific evidence 63, 83, 99, 128, 138 social see also research benefits, 206 Scleropages leichardti principles, 151, 173 see saratoga soft-stemmed pondweed, 85 seasonal, 27, 45, 94, 105, 106, 116, 134, 155, software, 116 206 soil types, 27 closures, 105, 106 solvent, 125 conditions, 45, 206 sonar-based techniques, 116 temperatures, 116 sonic imaging, 116 sediments, 27, 28, 37, 59, 63, 78, 82, 83, 117, South Australia, 18, 26, 27, 31, 38, 39, 40, 56, 118, 120, 146, 161 60, 62, 64, 66, 69, 70, 72, 73, 74, 88, 91, cattle access points, 27 93, 95, 102, 106, 124, 126, 128 loads, 78, 83 distribution of carp, 31 particles, 120, 161 introduction of carp, 18 resuspension, 82 legislation, 100, 106 seedbanks, 120 South Australian Field and Game Association seeds, 40, 63 (SAFGA), 66 Sepik River, 58 South Australian Research and Development sequential depletion, 117 Institute (SARDI), 106, 124 Settlers Creek Landcare Group, 63, 64 south-east Asia, 11, 13, 55 Seven Creeks, 29, 30 southern bluefin tuna, 121 Severn River, 31 southern purple-spotted gudgeon, 56 sexual maturity, 44, 130 southern pygmy perch, 87 shiners, 15 Spain, 92 shires, 170, 172 spangled perch, 58 Shoalhaven River, 25 spatial scale, 80, 111, 121 short-finned eel, 58 spawning, 27, 28, 37, 38, 41, 42, 43, 44, 45, 54, 82, 83, 95, 105, 108, 124, 129, 144, short-term strategy, 144 153, 161, 177, 178, 181 Siberia, 13 abundance, 44 side-scan sonar, 116 behaviour, 41 silt, 28, 63 locations, 54 siltation, 27, 56, 124, 147 period, 42, 105 silver bream, 14 permanent, 67 silver carp, 12, 14 season, 41, 42, 144 silver perch, 52, 56, 57, 58, 66, 69, 70, 83, 87 sites, 27, 54, 82 Singapore, 19, 20 stock, 43

Managing the Impacts of Carp 245 suitable habitats, 41 storm events, 83 species richness, 55, 86, 87 strategic approach, 7, 138, 169, 175, 176 sperm, 41 see also management and control Sphaerospora cyprini strategic management, 7, 8, 9, 138, 140, 145, see kidney diease 152 spines of carp, 34 see also management and control Spirogyra sp. Strategic Research Plan, 60 see filamentous algae stratified survey design, 115 spread of carp, 7, 11, 12, 17, 23, 24, 26, 27, streamside vegetation, 75 30, 31, 32, 56, 57, 61, 64, 99, 102, 103, submerged vegetation, 43, 85, 124 107, 108, 109, 126, 128, 130, 134, 138, subsidies, 122 141, 142, 143, 151, 176, 177, 206 harvesting, 122 anabranches, 24, 29, 52, 124 substrate, 27, 41, 78, 120, 124, 161 billabongs, 24, 27, 29, 37, 40, 45, 52, 82, suitable habitats, 43, 44 85, 87, 95, 118, 120, 121, 151 superphosphate, 28 floods, 24, 27, 28, 39, 43, 44, 45, 48, 52, 54, 66, 67, 95, 113, 123, 141, 143, 155 survey, 31, 62, 78, 134, 135 live fish as bait, 26 survival, 17, 18, 38, 41, 43, 44, 45, 46, 61, 73, 83, 112, 122, 134, 143 weirs, 20, 24, 26, 27, 31, 48, 56, 130, 131 survival to recruitment, 44 Spring Carp Mortality Syndrome, 48 SVCV Spring Viraemia of Carp Virus (SVCV), 48, 49, 87, 99, 126 see Spring Viraemia of Carp Virus clinical signs, 127 swamps, 31 stakeholders, 7, 70, 74, 138, 152, 157, 159, Swan River, 31, 32 167, 168, 170, 173, 176, 182 swimbladders, 38 standardisation of monitoring, 145 sword tails, 19 standardised biological surveys, 112 Sydney Aquarium Society, 18 Standing Committee on Agriculture and Sydney fish markets, 74 Resource Management (SCARM), 7 synergist, 125 standing stock, 53, 93 T State and Territory agencies, 99, 101 table fish, 61, 91 statistical methods, 120 tagged carp release, 52 statistics, 120, 146, 147 Tambo River, 36 sterility, 129, 130 Tandanus tandanus stock see freshwater catfish access, 28, 62, 64, 117, 147, 161 Tasmania, 19, 20, 21, 24, 25, 32, 38, 45, 60, assessments, 93, 113 70, 78, 79, 102, 107, 108, 109, 124, 125, stocking 128, 141, 142, 177 campaign, 107 distribution of carp, 32 manipulations, 54 introduction of carp, 19, 20, 107 stocks of carp, 95 legislation, 100, 107 storage, 61, 91, 94, 96, 134 Tasmanian Inland Fisheries Commission, 59, 100 freezer facilities, 89, 91, 94, 96 Tasmanian lakes, 26, 78 releases, 134 technical feasibility, 140

246 Bureau of Rural Sciences technology, 71, 116, 117, 130 turbidity, 27, 37, 39, 55, 63, 72, 75, 79, 80, 81, temperature, 38, 45, 48, 59, 96, 116 82, 83, 85, 86, 87, 109, 111, 116, 117, 120, 125, 139, 140, 143, 147, 158, 162, 172, 178 fluctuations, 48 light penetration, 27, 55, 82, 83, 147 regimes, 45, 59 sediments, 27, 28, 37, 39, 41, 55, 78, 81, water temperatures, 28, 29, 38, 42, 45, 48, 82, 83, 112, 118, 120, 125, 146, 147, 171 52, 54, 58, 66 Typha, 159 tench, 12, 15, 16, 17, 18, 19, 27, 28 terrestrial, 27, 28, 40, 41, 68, 125, 129, 143 U undercutting of banks, 63, 81, 147 vertebrate pest species, 125 United Kingdom, 17, 48, 73 testosterone, 130 United States of America, 17, 73, 84, 86, 102, The Centennial Park Trust, 105 126 theoretical stock-recruitment, 43 universities, 17, 31, 38, 59, 60, 92, 133, 168, Thunnus maccoyii 175 see southern bluefin tuna urban lakes, 32, 107 tilapia, 19, 109 V timber harvesting, 28 Vallisneria sp. time-scales, 206 see ribbonweed Tinca tinca valuation techniques, 149 see tench value-adding, 88, 89, 94, 95, 170, 176 tissue parasite, 49 ventral fin, 34 Torrens River, 18, 31 variegated pygmy perch, 84 Torrumbarry, 52, 131 vegetated habitats, 37, 54 Total Catchment Management Committee, vegetation, 27, 28, 41, 56, 58, 61, 63, 64, 66, 170 84, 85, 106, 117, 118, 140, 147, 152, 153 tourism, 70, 78, 79, 150, 206 removal, 38 toxicants, 37 Vertebrate Pests Committee (VPC), 7 trading, 8, 105, 109, 127, 181 Victoria, 17, 18, 19, 20, 23, 24, 26, 27, 29, 30, transient, 143 40, 41, 42, 45, 56, 60, 62, 63, 64, 65, 66, translocations, 19, 109 67, 68, 69, 70, 71, 73, 74, 78, 79, 82, 85, 87, 88, 91, 92, 93, 95, 102, 103, 125, 128, transport, 91, 95, 102, 104, 106, 131, 141 133, 135, 170, 173, 176 systems, 104 Acclimatisation Society, 17 travel cost analysis, 149 distribution of carp, 29, 30, 103 tree collapse, 63, 64, 81 introduction of carp, 17, 18, 20, 23, 102 trials, 8, 128, 180, 181 legislation, 100, 103 Trichodinella sp., Tricholdina domerguei Victoria Market, 74 see Tricholdiniasis Victorian Carp Program, 29, 54, 79 Tricholdiniasis, 50 Victorian Carp Project, 99 trichopterans, 86 Victorian Department of Fisheries and tropical Australia, 56, 58 Wildlife, 23 trout, 17, 18, 26, 28, 32, 54, 56, 58, 62, 65, 66, Victorian Department of Natural Resources 70, 78, 84, 92, 125 and Environment, 59, 93, 161, 163 see also brown trout, rainbow trout, Victorian Fisheries Policy, 103 game fish Victorian Government, 18, 29, 66 trout cod, 56, 58, 66, 84

Managing the Impacts of Carp 247 Victorian Museum, 18 waterfowl, 23 Victorian Recreational Fishing Peak Body Waterwatch Program, 64, 163, 171, 173 (VRFish), 71, 103, 172 Waterwatch Victoria, 173 video, 116 waterways, 121 viral control agents, 7, 28, 67, 68, 69, 71, 87, Waterweek, 173 126, 127, 150, 181 weakness disease, 49 rhabdoviruses, 127 weirs, 20, 24, 26, 27, 31, 48, 56, 130, 131 viruses, 65, 67, 81, 126, 144, 151, 181 Wesley River, 31 W Western Australia, 19, 20, 21, 25, 31, 32, 109 Wagga Wagga, 74, 101 carp management, 109 Wakefield River, 31 distribution of carp, 31 Wannon River, 36 introduction of carp, 19 Warrego River, 24, 31 legislation, 100, 109 wastewater treatment systems, 71 western carp gudgeon, 54, 87 water wetlands, 23, 24, 27, 29, 31, 37, 48, 63, 66, 67, acidic, 125 77, 79, 86, 88, 101, 106, 117, 128, 134, authorities, 64, 141 138, 139, 140, 149, 152, 158, 169, 173, draw-down, 134 179, 181 extraction, 62, 81 drainage, 27 water levels, 24, 52, 66, 83, 124, 126, 134, temporary, 29 144, 180 wetting and drying cycle, 29 managers, 104, 173, 205, 206 White bream, 14 minimum water temperatures, 42 whitespot, 50 muddiness, 23 wholesale, 74, 88, 91 quality, 61, 63, 64, 70, 72, 75, 78, 79, 81, price, 74, 88 96, 118, 120, 123, 124, 134, 138, 139, 140, willows, 28, 29 150, 152, 154, 156, 161, 162, 163, 173, leaf fall, 28 178, 205, 206 root masses, 28 poor water quality, 37, 38, 87, 124 Wimmera River, 24, 29 resources, 26, 27, 29 Wingecarribee Reservoir, 30, 126 flow cycle, 27 workshops, 74, 170, 176, 205 flow events, 133, 155 world markets, 92 irrigation channels, 19, 26, 30, 31, 78, 80, 121, 134, 139, 140 worms, 28 reservoirs, 18, 26, 37, 92, 126 X storages, 30, 53, 93, 117, 170 Xiphophorus helleri chemical treatment, 117 see sword tails velocity, 37, 120 Y users, 62, 78 yabbies, 69, 105 Water Allocation Management Process, Yallourn Storage Dam, 23 29 Yanco strain, 19, 21 watering livestock, 62 Yarra pygmy perch, 56, 84 watersheds, 106 Yarra River, 18, 73 water rats, 84 Yarrawonga Weir, 131 Yorta Yorta community, 67, 68

248 Bureau of Rural Sciences Z zone system, 182 Zoological Society of Victoria, 17 zooplankton, 39, 40, 43, 53, 54, 55, 82, 86, 122, 179 grazing, 127 zooplanktivorous, 127

Managing the Impacts of Carp 249 Introduced carp dominate fish communities throughout many waterways in south- eastern Australia. They also occur in Western Australia and Tasmania and have the potential to spread through many more of Australia’s water systems. Carp could eventually become widespread throughout the country. Carp are known to damage aquatic plants and increase water turbidity but their impacts on native fish species are not yet clear. Carp are also a commercial and recreational fishing resource. Managing the Impacts of Carp provides a comprehensive review of the history of carp in Australia, their biology, the damage they cause and community attitudes to these problems and their solutions. Key strategies for successful carp management are recommended by the authors who are scientific experts in carp management. These strategies are illustrated by case studies. Managing the Impacts of Carp is an essential guide for policy makers, land and water managers, carp fishers and all others interested in carp management.